Reinsurance Group of America (RGA) 10-K 27 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document And Entitiy Information [Abstract]
Document type	10-K
Document period end date	Dec. 31, 2017
Amendment flag	false
Entity registrant name	REINSURANCE GROUP OF AMERICA INC
Entity central index key	898,174
Entity current reporting status	Yes
Entity voluntary filers	No
Current fiscal year end date	--12-31
Entity filer category	Large Accelerated Filer
Entity well known seasoned issuer	Yes
Common Shares Outstanding		64,481,393
Entity public float			$ 8.3
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fixed Maturity Securities [Abstract]
Available-for-sale at fair value (amortized cost of $35,281,412 and $30,211,787)	$ 38,150,820	$ 32,093,625
Mortgage loans on real estate (net of allowances of $9,384 and $7,685)	4,400,533	3,775,522
Policy loans	1,357,624	1,427,602
Funds withheld at interest	6,083,388	5,875,919
Short-term investments	93,304	76,710
Other invested assets	1,605,484	1,591,940
Total investments	51,691,153	44,841,318
Cash and cash equivalents	1,303,524	1,200,718
Accrued investment income	392,721	347,173
Premiums receivable and other reinsurance balances	2,338,481	1,930,755
Reinsurance ceded receivables	782,027	683,972
Deferred policy acquisition costs	3,239,824	3,338,605
Other assets	767,088	755,338
Total assets	60,514,818	53,097,879
Liabilities and Stockholders’ Equity
Future policy benefits	22,363,241	19,581,573
Interest-sensitive contract liabilities	16,227,642	14,029,354
Other policy claims and benefits	4,992,074	4,263,026
Other reinsurance balances	488,739	388,989
Deferred income taxes	2,198,309	2,770,640
Other liabilities	1,102,975	1,041,880
Long-term debt	2,788,365	3,088,635
Collateral finance and securitization notes	783,938	840,700
Total liabilities	50,945,283	46,004,797
Commitments and contingent liabilities (See Note 12)
Stockholders Equity:
Preferred stock (par value $.01 per share; 10,000,000 shares authorized; no shares issued or outstanding)	0	0
Common stock (par value $.01 per share; 140,000,000 shares authorized; shares issued: 79,137,758 at December 31, 2017 and 2016)	791	791
Additional paid-in-capital	1,870,906	1,848,611
Retained earnings	6,736,265	5,199,130
Treasury stock, at cost - 14,685,663 and 14,835,256 shares	(1,102,058)	(1,094,779)
Accumulated other comprehensive income	2,063,631	1,139,329
Total stockholders’ equity	9,569,535	7,093,082
Total liabilities and stockholders’ equity	$ 60,514,818	$ 53,097,879

CONSOLIDATED BALANCE SHEETS PAR

CONSOLIDATED BALANCE SHEETS PARENTHETICAL - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Available for Sale at Fair value - Amortized cost	$ 35,281,412	$ 30,211,787
Preferred stock par value	$ 0.01	$ 0.01
Preferred stock shares authorized	10,000,000	10,000,000
Preferred stock shares issued	0	0
Preferred stock shares outstanding	0	0
Common stock par value	$ 0.01	$ 0.01
Common stock shares authorized	140,000,000	140,000,000
Common Stock, Shares, Issued	79,137,758	79,137,758
Common stock shares outstanding	64,452,095	64,302,502
Treasury Shares Held	14,685,663	14,835,256
Allowances for Loan and Lease Losses, Real Estate	$ 9,384	$ 7,685

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Net premiums	$ 9,841,130	$ 9,248,871	$ 8,570,741
Investment income, net of related expenses	2,154,651	1,911,886	1,734,495
Investment related gains (losses), net:
Other-than-temporary impairments on fixed maturity securities	(42,639)	(38,805)	(57,380)
Other-than-temporary impairments on fixed maturity securities transferred to other comprehensive income	0	74	0
Other investment related gains (losses), net	210,519	132,926	(107,370)
Total investment related gains (losses), net	167,880	94,195	(164,750)
Other revenues	352,108	266,559	277,692
Total revenues	12,515,769	11,521,511	10,418,178
Benefits and expenses
Claims and other policy benefits	8,518,917	7,993,375	7,489,382
Interest credited	502,040	364,691	336,964
Policy acquisition costs and other insurance expenses	1,466,646	1,310,540	1,127,486
Other operating expenses	710,690	645,509	554,044
Interest expense	146,025	137,623	142,863
Collateral finance and securitization expense	28,636	25,827	22,644
Total benefits and expenses	11,372,954	10,477,565	9,673,383
Income before income taxes	1,142,815	1,043,946	744,795
Provision for income taxes	(679,366)	342,503	242,629
Net income	$ 1,822,181	$ 701,443	$ 502,166
Earnings per share
Basic earnings per share (in dollars per share)	$ 28.28	$ 10.91	$ 7.55
Diluted earnings per share (in dollars per share)	27.71	10.79	7.46
Dividends declared per share	$ 1.82	$ 1.56	$ 1.40

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Comprehensive income
Net Income (Loss) Attributable to Parent	$ 1,822,181	$ 701,443	$ 502,166
Other comprehensive income (loss), net of tax:
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	69,126	8,610	(262,998)
Net unrealized investment gains (losses)	698,078	419,336	(689,076)
Change in other-than-temporary impairment losses on fixed maturity securities	(244)	(947)
Defined benefit pension and postretirement plan adjustments	726	3,099	3,229
Total other comprehensive income (loss), net of tax	767,930	431,045	(948,845)
Total comprehensive income (loss)	$ 2,590,111	$ 1,132,488	$ (446,679)

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock Member	Additional Paid In Capital Member	Retained Earnings Member	Treasury Stock Member	Accumulated Other Comprehensive Income Member
Total stockholders equity at Dec. 31, 2014	$ 7,023,452	$ 791	$ 1,798,279	$ 4,239,647	$ (672,394)	$ 1,657,129
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	502,166			502,166
Other Comprehensive Income (Loss), Net of Tax	(948,845)					(948,845)
Dividends to stockholders	(93,381)			(93,381)
Purchase of treasury stock	(384,519)				(384,519)
Reissuance of treasury stock	(36,508)		(17,863)	(28,129)	(46,774)
Total stockholders equity at Dec. 31, 2015	6,135,381	791	1,816,142	4,620,303	(1,010,139)	708,284
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	701,443			701,443
Other Comprehensive Income (Loss), Net of Tax	431,045					431,045
Dividends to stockholders	(100,371)			(100,371)
Purchase of treasury stock	(122,916)				(122,916)
Reissuance of treasury stock	(48,500)		(32,469)	(22,245)	(38,276)
Total stockholders equity at Dec. 31, 2016	7,093,082	791	1,848,611	5,199,130	(1,094,779)	1,139,329
Increase (Decrease) in Stockholders' Equity [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | Accounting Standards Update 2018 02 [Member]	17,723			(138,649)		156,372
Net Income (Loss) Attributable to Parent	1,822,181			1,822,181
Other Comprehensive Income (Loss), Net of Tax	767,930					767,930
Dividends to stockholders	(117,291)			(117,291)
Purchase of treasury stock	(43,508)				(43,508)
Reissuance of treasury stock	(29,418)		(22,295)	(29,106)	(36,229)
Total stockholders equity at Dec. 31, 2017	$ 9,569,535	$ 791	$ 1,870,906	$ 6,736,265	$ (1,102,058)	$ 2,063,631

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Cash flows from operating activities
Net Income (Loss) Attributable to Parent	$ 1,822,181	$ 701,443	$ 502,166
Change in operating assets and liabilities:
Accrued investment income	(43,142)	(18,761)	(48,458)
Premiums receivable and other reinsurance balances	(346,737)	(156,836)	(313,882)
Deferred policy acquisition costs	154,234	31,024	(66,633)
Reinsurance ceded receivable balances	(124,056)	(53,221)	(11,740)
Future policy benefits, other policy claims and benefits, and other reinsurance balances	1,320,810	810,474	1,867,488
Deferred income taxes	(847,304)	293,777	148,996
Other assets and other liabilities, net	242,466	(98,675)	(55,345)
Amortization of net investment premiums, discounts and other	(105,382)	(93,952)	(77,303)
Depreciation, Depletion and Amortization	52,902	26,853	31,103
Investment related (gains) losses, net	(167,880)	(94,195)	164,750
Excess tax benefits from share-based payment arrangement	0	(162)	(2,963)
Other, net	24,216	117,949	(49,564)
Net cash provided by operating activities	1,982,308	1,465,718	2,088,615
Cash flows from investing activities
Sales of fixed maturity securities available-for-sale	7,308,608	4,584,828	5,461,687
Principal payments on mortgage loans on real estate	589,214	472,435	439,640
Proceeds from Sale of Available-for-sale Securities, Equity	207,347	434,518	81,319
Proceeds from Sale and Collection of Mortgage Notes Receivable	339,919	442,755	383,828
Proceeds from Collection of Policy Loans	114,586	88,840	21,322
Payments to Acquire Available-for-sale Securities	(8,941,293)	(7,414,647)	(5,874,309)
Payments to Acquire Available-for-sale Securities, Equity	(81,254)	(584,532)	(95,834)
Purchases of fixed maturity securities available-for-sale	(964,421)	(1,092,876)	(810,092)
Payments to Fund Policy Loans	(44,607)	(47,646)	(52,207)
Cash invested in funds withheld at interest	(22,557)	(32,597)	(339,062)
Purchase of businesses, net of cash acquired of $69,823	0	0	(145,235)
Payments to Acquire Property, Plant, and Equipment	(44,211)	(44,642)	(23,553)
Increase (Decrease) in Payables under Repurchase Agreements	0	0	(101,203)
Change in short-term investments	52,302	465,628	(470,002)
Change in other invested assets	(121,206)	(97,790)	91,960
Net cash used in investing activities	(1,607,573)	(2,825,726)	(1,431,741)
Cash flows from financing activities
Dividends to stockholders	(117,291)	(100,371)	(93,381)
Repayment of collateral finance and securitization notes	(68,429)	(64,571)	(19,732)
Proceeds from Issuance of Secured Debt	0	0	164,220
Proceeds from long-term debt issuance	0	799,984	0
Debt issuance costs	0	(8,766)	(4,748)
Principal payments of long-term debt	(302,582)	(2,479)	(2,380)
Purchases of treasury stock	(43,508)	(122,916)	(384,519)
Excess tax benefits from share-based payment arrangement	0	162	2,963
Exercise of stock options, net	7,292	15,321	11,151
Change in cash collateral for derivative positions and other arrangements	(65,422)	26,413	52,381
Deposits on universal life and other investment type policies and contracts	1,017,699	1,041,623	277,280
Withdrawals on universal life and other investment type policies and contracts	(752,381)	(529,011)	(711,517)
Net cash used in financing activities	(324,622)	1,055,389	(708,282)
Effect of exchange rate changes on cash	52,693	(19,938)	(68,986)
Change in cash and cash equivalents	102,806	(324,557)	(120,394)
Cash and cash equivalents, beginning of period	1,200,718	1,525,275	1,645,669
Cash and cash equivalents, end of period	1,303,524	1,200,718	1,525,275
Supplementary information:
Interest paid	173,471	156,727	148,124
Income taxes paid, net of refunds	37,098	61,085	41,577
Transfer to Investments	3,285,837	120,500	2,092,558
Capital Expenditures Incurred but Not yet Paid	0	0	253
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	0	0	(3,894,940)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	$ 0	$ 0	$ 4,040,175

CONSOLIDATED STATEMENTS OF CAS8

CONSOLIDATED STATEMENTS OF CASH FLOWS CONSOLIDATED STATEMENTS OF CASH FLOWS PARENTHETICAL - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Cash Flows [Abstract]
Cash Acquired from Acquisition	$ 0	$ 0	$ 69,823

Business and Basis of Presentat

Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Basis of Presentation	BUSINESS AND BASIS OF PRESENTATION Business Reinsurance Group of America, Incorporated (“RGA”) is an insurance holding company that was formed on December 31, 1992. The consolidated financial statements herein include the assets, liabilities, and results of operations of RGA and its subsidiaries, all of which are wholly owned (collectively, the “Company”). The Company is engaged in providing traditional reinsurance, which includes individual and group life and health, disability, and critical illness reinsurance. The Company also provides financial solutions, which includes longevity reinsurance, asset-intensive products, primarily annuities, and financial reinsurance. Reinsurance is an arrangement under which an insurance company, the reinsurer, agrees to indemnify another insurance company, the ceding company, for all or a portion of the insurance risks underwritten by the ceding company. Reinsurance is designed to (i) reduce the net liability on individual risks, thereby enabling the ceding company to increase the volume of business it can underwrite, as well as increase the maximum risk it can underwrite on a single life or risk; (ii) stabilize operating results by leveling fluctuations in the ceding company’s loss experience; (iii) assist the ceding company to meet applicable regulatory requirements; and (iv) enhance the ceding company’s financial strength and surplus position. Basis of Presentation The consolidated financial statements of the Company have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosures of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The most significant estimates include those used in determining deferred policy acquisition costs, premiums receivable, future policy benefits, incurred but not reported claims, income taxes, valuation of investments and investment impairments, and valuation of embedded derivatives. Actual results could differ materially from the estimates and assumptions used by management. The accompanying consolidated financial statements include the accounts of RGA and its subsidiaries, all of which are wholly owned, and any variable interest entities where the Company is the primary beneficiary. Entities in which the Company has significant influence over the operating and financing decisions but are not required to be consolidated are reported under the equity method of accounting. The Company evaluates variable interest entities in accordance with the general accounting principles for Consolidation . Intercompany balances and transactions have been eliminated. There were no subsequent events that would require disclosure or adjustments to the accompanying consolidated financial statements through the date the consolidated financial statements were issued.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Investments Fixed Maturity Securities Fixed maturity securities classified as available-for-sale are reported at fair value and are so classified based upon the possibility that such securities could be sold prior to maturity if that action enables the Company to execute its investment philosophy and appropriately match investment results to operating and liquidity needs. Unrealized gains and losses on fixed maturity securities classified as available-for-sale, less applicable deferred income taxes as well as related adjustments to deferred acquisition costs, if applicable, are reflected as a direct charge or credit to accumulated other comprehensive income (“AOCI”) in stockholders’ equity on the consolidated balance sheets. Investment income is recognized as it accrues or is legally due. Realized gains and losses on sales of investments are included in investment related gains (losses), net, as are credit impairments that are other-than-temporary in nature. The cost of investments sold is primarily determined based upon the specific identification method. Mortgage Loans on Real Estate Mortgage loans on real estate are carried at unpaid principal balances, net of any unamortized premium or discount and valuation allowances. Interest income is accrued on the principal amount of the mortgage loan based on its contractual interest rate. Amortization of premiums and discounts is recorded using the effective yield method. The Company accrues interest on loans until it is probable the Company will not receive interest or the loan is 90 days past due. Interest income, amortization of premiums, accretion of discounts and prepayment fees are reported in investment income, net of related expenses in the consolidated statements of income. A mortgage loan is considered to be impaired when, based on the current information and events, it is probable that the Company will be unable to collect all amounts due according to the contractual terms of the mortgage agreement. Although all available and applicable factors are considered in the Company’s analysis, loan-to-value and debt service coverage ratios are the most critical factors in determining impairment. Valuation allowances on mortgage loans are established based upon inherent losses expected by management to be realized in connection with future dispositions or settlement of mortgage loans, including foreclosures. The Company establishes valuation allowances for estimated impairments on an individual loan basis as of the balance sheet date. Such valuation allowances are based on the excess carrying value of the loan over the present value of expected future cash flows discounted at the loan’s original effective interest rate, the value of the loan’s collateral if the loan is in the process of foreclosure or is otherwise collateral-dependent, or the loan’s market value if the loan is being sold. Non-specific valuation allowances are established for mortgage loans based upon several loan factors, including the Company’s historical experience for loan losses, defaults and loss severity, loss expectations for loans with similar risk characteristics and industry statistics. These evaluations are revised as conditions change and new information becomes available. In addition to historical experience, management considers qualitative factors that include the impact of changing macro-economic conditions, which may not be currently reflected in the loan portfolio performance, and the quality of the loan portfolio. Any interest accrued or received on the net carrying amount of the impaired loan will be included in investment income or applied to the principal of the loan, depending on the assessment of the collectability of the loan. Mortgage loans deemed to be uncollectible or that have been foreclosed are charged off against the valuation allowances and subsequent recoveries, if any, are credited to the valuation allowances. Changes in valuation allowances are reported in investment related gains (losses), net on the consolidated statements of income. The Company evaluates whether a mortgage loan modification represents a troubled debt restructuring. In a troubled debt restructuring, the Company grants concessions related to the borrower’s financial difficulties. Generally, the types of concessions include: reduction of the contractual interest rate, extension of the maturity date at an interest rate lower than current market interest rates and/or a reduction of accrued interest. The Company considers the amount, timing and extent of the concession granted in determining any impairment or changes in the specific valuation allowance recorded in connection with the troubled debt restructuring. Through the continuous monitoring process, the Company may have recorded a specific valuation allowance prior to when the mortgage loan is modified in a troubled debt restructuring. Accordingly, the carrying value (after specific valuation allowance) before and after modification through a troubled debt restructuring may not change significantly, or may increase if the expected recovery is higher than the pre-modification recovery assessment. Policy Loans Policy loans are reported at the unpaid principal balance. Interest income on such loans is recorded as earned using the contractually agreed-upon interest rate. These policy loans present no credit risk because the amount of the loan cannot exceed the obligation due the ceding company upon the death of the insured or surrender of the underlying policy. Funds Withheld at Interest Funds withheld at interest represent amounts contractually withheld by ceding companies in accordance with reinsurance agreements. For agreements written on a modified coinsurance basis and agreements written on a coinsurance funds withheld basis, assets which support the net statutory reserves or as defined in the treaty, are withheld and legally owned by the ceding company. Interest, recorded in investment income, net of related expenses in the consolidated statements of income, accrues to these assets at calculated rates as defined by the treaty terms. Changes in the value of the equity options held within the funds withheld portfolio associated with equity-indexed annuity treaties are reflected in investment income, net of related expenses. Short-term Investments Short-term investments represent investments with remaining maturities greater than three months but less than twelve months, at the date of purchase, and are stated at estimated fair value or amortized cost, which approximates estimated fair value. Interest on short-term investments is recorded in investment income, net of related expenses in the consolidated statements of income. Other Invested Assets In addition to derivative contracts discussed below, other invested assets include equity securities, contractholder-directed investments, limited partnership interests, joint ventures (other than operating joint ventures), equity release mortgages and structured loans. Equity securities are carried at fair value with the exception of the Company’s investment in the Federal Home Loan Bank of Des Moines (“FHLB”) common stock, which is carried at cost. The fair value option (“FVO”) was elected for contractholder-directed investments supporting unit-linked variable annuity type liabilities which do not qualify for presentation and reporting as separate accounts. Changes in estimated fair value of these securities are included in investment income, net of related expenses. Limited partnership interests and structured loans are primarily carried at cost. Based on the nature and structure of these investments, they do not meet the characteristics of an equity security in accordance with applicable accounting standards. Joint ventures and certain limited partnerships are reported using the equity method of accounting. Equity release mortgages are carried at unpaid principal balances, net of any unamortized premium or discount and valuation allowance. Interest income is accrued on the principal amount of the equity release mortgage based on its contractual interest rate. Securities Borrowing, Lending and Repurchase Agreements The Company participates in securities borrowing programs whereby securities, which are not reflected on the Company’s consolidated balance sheets, are borrowed from third parties. The borrowed securities are used to provide collateral under affiliated reinsurance transactions. The Company is required to maintain a minimum of 100% of the fair value, or par value under certain programs, of the borrowed securities as collateral. The collateral consists of rights to reinsurance treaty cash flows. If cash flows from the reinsurance treaties are insufficient to maintain the minimum collateral requirement, the Company may substitute cash or securities to meet the requirement. The Company participates in a securities lending program whereby securities, reflected as investments on the Company’s consolidated balance sheets, are loaned to a third party. The Company receives securities as collateral, in an amount equal to a minimum of 105% of the fair value of the securities lent. The securities received as collateral are not reflected on the Company’s consolidated balance sheets. The Company participates in a repurchase program in which securities, reflected as investments on the Company’s consolidated balance sheets, are pledged to a third party. In return, the Company receives cash from the third party, which is reflected as a payable to a third party, included in other liabilities on the consolidated balance sheets. The Company is required to maintain a minimum collateral balance with a fair value of 102% of the cash received. The Company participates in repurchase/reverse repurchase programs in which securities, reflected as investments on the Company’s consolidated balance sheets, are pledged to third parties. In return, the Company receives securities from the third parties with an estimated fair value equal to a minimum of 100% of the securities pledged. The securities received are not reflected on the Company’s consolidated balance sheets. Other-than-Temporary Impairment The Company identifies fixed maturity and equity securities that could potentially have credit impairments that are other-than-temporary by monitoring market events that could impact issuers’ credit ratings, business climates, management changes, litigation, government actions and other similar factors. The Company also monitors late payments, pricing levels, rating agency actions, key financial ratios, financial statements, revenue forecasts and cash flow projections as indicators of credit issues. The Company reviews all securities on a case-by-case basis to determine whether an other-than-temporary decline in value exists and whether losses should be recognized. The Company considers relevant facts and circumstances in evaluating whether a credit or interest rate-related impairment of a security is other-than-temporary. Relevant facts and circumstances considered include: (1) the extent and length of time the fair value has been below cost; (2) the reasons for the decline in fair value; (3) the issuers financial position and access to capital; and (4) for fixed maturity securities, the Company’s intent to sell a security or whether it is more likely than not it will be required to sell the security before the recovery of its amortized cost which, in some cases, may extend to maturity and for equity securities, the Company’s ability and intent to hold the security for a period of time that allows for the recovery in value. To the extent the Company determines that a security is deemed to be other-than-temporarily impaired, an impairment loss is recognized. Impairment losses on equity securities are reported in investment related gains (losses), net on the consolidated statements of income. Impairment losses on fixed maturity securities recognized in the financial statements are dependent on the facts and circumstances related to the specific security. If the Company intends to sell a security or it is more likely than not that it would be required to sell a security before the recovery of its amortized cost, less any recorded credit loss, it recognizes an other-than-temporary impairment in investment related gains (losses), net on the consolidated statements of income for the difference between amortized cost and fair value. If neither of these two conditions exists then the recognition of the other-than-temporary impairment is bifurcated and the Company recognizes the credit loss portion in investment related gains (losses), net and the non-credit loss portion in AOCI. The Company estimates the amount of the credit loss component of a fixed maturity security impairment as the difference between amortized cost and the present value of the expected cash flows of the security. The present value is determined using the best estimate cash flows discounted at the effective interest rate implicit to the security at the date of purchase or the current yield to accrete an asset-backed or floating rate security. The techniques and assumptions for establishing the best estimate cash flows vary depending on the type of security. The asset-backed securities’ cash flow estimates are based on security-specific facts and circumstances that may include collateral characteristics, expectations of delinquency and default rates, loss severity and prepayment speeds and structural support, including subordination and guarantees. The corporate fixed maturity security cash flow estimates are derived from scenario-based outcomes of expected corporate restructurings or the disposition of assets using security specific facts and circumstances including timing, security interests and loss severity. In periods after an other-than-temporary impairment loss is recognized on a fixed maturity security, the Company will report the impaired security as if it had been purchased on the date it was impaired and will continue to estimate the present value of the estimated cash flows of the security. Accordingly, the discount (or reduced premium) based on the new cost basis is accreted into net investment income over the remaining term of the fixed maturity security in a prospective manner based on the amount and timing of estimated future cash flows. The Company considers its cost method investments for other-than-temporary impairment when the carrying value of these investments exceeds the net asset value. The Company takes into consideration the severity and duration of this excess when deciding if the cost method investment is other-than-temporarily impaired. For equity method investments (including real estate ventures), the Company considers financial and other information provided by the investee, other known information and inherent risks in the underlying investments, as well as future capital commitments, in determining whether an impairment has occurred. Derivative Instruments Overview The Company utilizes a variety of derivative instruments including swaps, options, forwards and futures, primarily to manage or hedge interest rate risk, credit risk, inflation risk, foreign currency risk, market volatility and various other market risks associated with its business. The Company does not invest in derivatives for speculative purposes. It is the Company’s policy to enter into derivative contracts primarily with highly rated parties. See Note 5 - “Derivative Instruments” for additional detail on the Company’s derivative positions. Accounting and Financial Statement Presentation of Derivatives Derivatives are carried on the Company’s consolidated balance sheets primarily in other invested assets or other liabilities, at fair value. Certain derivatives are subject to master netting provisions and reported as a net asset or liability. On the date a derivative contract is executed, the Company designates the derivative as (1) a fair value hedge, (2) a cash flow hedge, (3) a net investment hedge in a foreign operation or (4) free-standing derivatives held for other risk management purposes, which primarily involve managing asset or liability risks associated with the Company’s reinsurance treaties which do not qualify for hedge accounting. Changes in the fair value of free-standing derivative instruments, which do not receive accounting hedge treatment, are primarily reflected in investment related gains (losses), net. Changes in the fair value of non-investment free-standing derivative instruments (e.g. mortality and longevity swaps), which do not receive accounting hedge treatment, are reflected in other revenues. Hedge Documentation and Hedge Effectiveness To qualify for hedge accounting, at the inception of the hedging relationship, the Company formally documents its risk management objective and strategy for undertaking the hedging transaction, as well as its designation of the hedge as either (i) a fair value hedge; (ii) a cash flow hedge; or (iii) a hedge of a net investment in a foreign operation. In this documentation, the Company sets forth how the hedging instrument is expected to hedge the designated risks related to the hedged item and sets forth the method that will be used to retrospectively and prospectively assess the hedging instrument’s effectiveness and the method which will be used to measure ineffectiveness. A derivative designated as a hedging instrument must be assessed as being highly effective in offsetting the designated risk of the hedged item. Hedge effectiveness is formally assessed at inception and periodically throughout the life of the designated hedging relationship. Under a fair value hedge, changes in the fair value of the hedging derivative, including amounts measured as ineffective, and changes in the fair value of the hedged item related to the designated risk being hedged, are reported within investment related gains (losses), net. The fair values of the hedging derivatives are exclusive of any accruals that are separately reported in the consolidated statement of income within interest income or interest expense to match the location of the hedged item. Under a cash flow hedge, changes in the fair value of the hedging derivative measured as effective are reported within AOCI and the deferred gains or losses on the derivative are reclassified into the consolidated statement of income when the Company’s earnings are affected by the variability in cash flows of the hedged item. Changes in the fair value of the hedging instrument measured as ineffective are reported within investment related gains (losses), net. The fair values of the hedging derivatives are exclusive of any accruals that are separately reported in the consolidated statement of income within interest income or interest expense to match the location of the hedged item. In a hedge of a net investment in a foreign operation, changes in the fair value of the hedging derivative that are measured as effective are reported within AOCI consistent with the translation adjustment for the hedged net investment in the foreign operation. Changes in the fair value of the hedging instrument measured as ineffective are reported within investment related gains (losses), net. The Company discontinues hedge accounting prospectively when: (i) it is determined that the derivative is no longer highly effective in offsetting changes in the estimated fair value or cash flows of a hedged item; (ii) the derivative expires, is sold, terminated, or exercised; (iii) it is no longer probable that the hedged forecasted transaction will occur; or (iv) the derivative is de-designated as a hedging instrument. When hedge accounting is discontinued because it is determined that the derivative is not highly effective, the derivative continues to be carried in the consolidated balance sheets at fair value, with changes in fair value recognized in investment related gains (losses), net. The carrying value of the hedged asset or liability under a fair value hedge is no longer adjusted for changes in its estimated fair value due to the hedged risk, and the cumulative adjustment to its carrying value is amortized into income over the remaining life of the hedged item. Provided the hedged forecasted transaction occurrence is still probable, the changes in estimated fair value of derivatives recorded in other comprehensive income (loss) (“OCI”) related to discontinued cash flow hedges are released into the consolidated statement of income when the Company’s earnings are affected by the variability in cash flows of the hedged item. When hedge accounting is discontinued because it is no longer probable that the forecasted transactions will occur on the anticipated date or within two months of that date, the derivative continues to be carried in the consolidated balance sheets at its estimated fair value, with changes in estimated fair value recognized currently in investment related gains (losses), net. Deferred gains and losses of a derivative recorded in OCI pursuant to the discontinued cash flow hedge of a forecasted transaction that is no longer probable are recognized immediately in investment related gains (losses), net. In all other situations in which hedge accounting is discontinued, the derivative is carried at its estimated fair value in the consolidated balance sheets, with changes in its estimated fair value recognized in the current period as investment related gains (losses), net. Embedded Derivatives The Company reinsures certain annuity products that contain terms that are deemed to be embedded derivatives, primarily equity-indexed annuities and variable annuities with guaranteed minimum benefits. The Company assesses reinsurance contract terms to identify embedded derivatives which are required to be bifurcated under the general accounting principles for Derivatives and Hedging . If the contract is not reported for in its entirety at fair value and it is determined that the terms of the embedded derivative are not clearly and closely related to the economic characteristics of the host contract, and that a separate instrument with the same terms would qualify as a derivative instrument, the embedded derivative is bifurcated from the host contract and accounted for separately. Such embedded derivatives are carried on the consolidated balance sheets at fair value in the same line item as the host contract. Changes in the fair value of embedded derivatives associated with equity-indexed annuities are reflected in interest credited on the consolidated statements of income and changes in the fair value of embedded derivatives associated with variable annuity guaranteed minimum benefits are reflected in investment related gains (losses), net on the consolidated statements of income. See “Interest-Sensitive Contract Liabilities” below for additional information on embedded derivatives related to equity-indexed and variable annuities. The Company has implemented an economic hedging strategy to mitigate the volatility associated with its reinsurance of variable annuity guaranteed minimum benefits. The hedging strategy is designed such that changes in the fair value of the hedge contracts, primarily futures, swap contracts and options, move in the opposite direction of changes in the fair value of the embedded derivatives. While the Company actively manages its hedging program, the hedges that are in place may not be totally effective in offsetting the embedded derivative changes due to the many variables that must be managed and the Company may see a corresponding increase or decrease in the net liability. The Company has elected not to assess this hedging strategy for hedge accounting treatment. Additionally, reinsurance treaties written on a modified coinsurance or funds withheld basis are subject to the general accounting principles for Derivatives and Hedging related to embedded derivatives. The Company’s funds withheld at interest balances are primarily associated with its reinsurance treaties structured on a modified coinsurance or funds withheld basis, the majority of which were subject to the general accounting principles for Derivatives and Hedging related to embedded derivatives. Management believes the embedded derivative feature in each of these reinsurance treaties is similar to a total return swap on the assets held by the ceding companies. The valuation of embedded derivatives is sensitive to the investment credit spread environment. Changes in investment credit spreads are also affected by the application of a credit valuation adjustment (“CVA”). The fair value calculation of an embedded derivative in an asset position utilizes a CVA based on the ceding company’s credit risk. Conversely, the fair value calculation of an embedded derivative in a liability position utilizes a CVA based on the Company’s credit risk. Generally, an increase in investment credit spreads, ignoring changes in the CVA, will have a negative impact on the fair value of the embedded derivative (decrease in income). The fair value of the embedded derivatives is included in the funds withheld at interest line item on the consolidated balance sheets. The change in the fair value of the embedded derivatives is recorded in investment related gains (losses), net on the consolidated statements of income. The Company has entered into various financial reinsurance treaties on a funds withheld and modified coinsurance basis. These treaties do not transfer significant insurance risk and are recorded on a deposit method of accounting with the Company earning a net fee. As a result of the experience refund provisions contained in these treaties, the value of the embedded derivatives in these contracts is currently considered immaterial. The Company monitors the performance of these treaties on a quarterly basis. Significant adverse performance or losses on these treaties may result in a loss associated with the embedded derivative. Fair Value Measurements General accounting principles for Fair Value Measurements and Disclosures define fair value, establish a framework for measuring fair value, establish a fair value hierarchy based on the inputs used to measure fair value and enhance disclosure requirements for fair value measurements. In compliance with these principles, the Company has categorized its assets and liabilities, based on the priority of the inputs to the valuation technique, into a three level hierarchy or separately for assets measured using the net asset value (“NAV”). The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1), the second highest priority to quoted prices in markets that are not active or inputs that are observable either directly or indirectly (Level 2) and the lowest priority to unobservable inputs (Level 3). If the inputs used to measure fair value fall within different levels of the hierarchy, the category level is based on the lowest priority level input that is significant to the fair value measurement of the asset or liability. See Note 6 - “Fair Value of Assets and Liabilities” for further details on the Company’s assets and liabilities recorded at fair value. Cash and Cash Equivalents Cash and cash equivalents include cash on deposit and highly liquid debt instruments purchased with an original maturity of three months or less. Premiums Receivable Premiums are accrued when due and in accordance with information received from the ceding company. When the Company enters into a new reinsurance agreement, it records accruals based on the terms of the reinsurance treaty. Similarly, when a ceding company fails to report information on a timely basis, the Company records accruals based on the terms of the reinsurance treaty as well as historical experience. Other management estimates include adjustments for increased in force on existing treaties, lapsed premiums given historical experience, the financial health of specific ceding companies, collateral value and the legal right of offset on related amounts (i.e. allowances and claims) owed to the ceding company. Under the legal right of offset provisions in its reinsurance treaties, the Company can withhold payments for allowances and claims from unpaid premiums. Based on its review of these factors and historical experience, the Company did not believe a provision for doubtful accounts was necessary as of December 31, 2017 or 2016 . Reinsurance Ceded Receivables The Company generally reports retrocession activity on a gross basis. Amounts paid or deemed to have been paid for reinsurance are reflected in reinsurance ceded receivables. The cost of reinsurance related to long-duration contracts is recognized over the terms of the reinsured policies on a basis consistent with the reporting of those policies. Deferred Policy Acquisition Costs Costs of acquiring new business, which vary with and are directly related to the production of new business, have been deferred to the extent that such costs are deemed recoverable from future premiums or gross profits. Such costs include commissions and allowances as well as certain costs of policy issuance and underwriting. Non-commission costs related to the acquisition of new and renewal insurance contracts may be deferred only if they meet the following criteria: • Incremental direct costs of a successful contract acquisition • Portions of employees’ salaries and benefits directly related to time spent performing specified acquisition activities for a contract that has been acquired or renewed • Other costs directly related to the specified acquisition or renewal activities that would not have been incurred had that acquisition contract transaction not occurred The Company tests the recoverability for each year of business at issue before establishing additional deferred acquisition costs (“DAC”). The Company also performs annual tests to establish that DAC are expected to remain recoverable, and if financial performance significantly deteriorates to the point where a deficiency exists, a cumulative charge to current operations will be recorded. No such adjustments related to DAC recoverability were made in 2017, 2016 and 2015 . DAC related to traditional life insurance contracts are amortized with interest over the premium-paying period of the related policies in proportion to the ratio of individual period premium revenues to total anticipated premium revenues over the life of the policy. Such anticipated premium revenues are estimated using the same assumptions used for computing liabilities for future policy benefits. DAC related to interest-sensitive life and investment-type policies are amortized over the lives of the policies, in proportion to the gross profits realized from mortality, investment income less interest credited, and expense margins. Other Reinsurance Balances The Company assumes and retrocedes financial reinsurance contracts that do not expose it to a reasonable possibility of loss from insurance risk. These contracts are reported as deposits and are included in other reinsurance assets/liabilities. The amount of revenue reported in other revenues on these contracts represents fees and the cost of insurance under the terms of the reinsurance agreement. Assets and liabilities are reported on a net or gross basis, depending on the specific details within each treaty. Reinsurance agreements reported on a net basis, where a legal right of offset exists, are generally included in other reinsurance balances on the consolidated balance sheets. Balances resulting from the assumption and/or subsequent transfer of benefits and obligations resulting from cash flows related to variable annuities have also been classified as other reinsurance balance assets and/or liabilities. Other reinsurance assets are included in premiums receivable and other reinsurance balances while other reinsurance liabilities are included in other reinsurance balances on the consolidated balance sheets. Goodwill and Value of Business Acquired Goodwill, reported in other assets, is not amortized into results of operations, but instead is reviewed at least annually for impairment and written down only in the periods in which the recorded value of goodwill exceeds its fair value. Goodwill as of December 31, 2017 and 2016 totaled $7.0 million . The value of business acquired (“VOBA”) is amortized in proportion to the ratio of annual premium revenues to total anticipated premium revenues or in relation to the present value of estimated profits. Anticipated premium revenues have been estimated using assumptions consis

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	ACQUISITIONS In April 2015, the Company completed the acquisition of 100% of Aurora National stock from Swiss Re Life & Health America, Inc. (“Swiss Re”) pursuant to the stock purchase agreement dated October 20, 2014, between the Company and Swiss Re. The transaction represented an opportunity to deploy capital into a seasoned closed block of business in the U.S. market. The total cash purchase price was $191.5 million , net of cash acquired. Total assets acquired were $3.7 billion , primarily consisting of $3.6 billion of investments, and total liabilities assumed were $3.5 billion . There is no goodwill, including tax deductible goodwill, associated with the acquisition. The business acquired is reflected in the U.S. and Latin America Traditional and Financial Solutions segments. This acquisition did not have a material impact on the Company’s consolidated financial statements, and as a result no proforma disclosures have been presented. In October 2015, the Company completed the acquisition of the life insurance portfolio of PGGM Levensverzekeringen, N.V. (“PGGM”), a Netherlands-based cooperative. This transaction supports the Company’s objective to capitalize on the realignment of the financial services industry and provide closed-block solutions in the European market. Total assets acquired were $404.4 million , primarily consisting of $395.6 million of investments, and total liabilities assumed were $394.1 million . There is no goodwill, including tax deductible goodwill, associated with the acquisition. The acquisition is reflected in the Company’s Europe, Middle East and Africa traditional and financial solutions segments. This acquisition did not have a material impact on the Company’s consolidated financial statements, and as a result no proforma disclosures have been presented.

Investments

Investments	12 Months Ended
	Dec. 31, 2017
Investments [Abstract]
Investments	INVESTMENTS Fixed Maturity and Equity Securities Available-for-Sale The Company holds various types of fixed maturity securities available-for-sale and classifies them as corporate securities (“Corporate”), Canadian and Canadian provincial government securities (“Canadian government”), residential mortgage-backed securities (“RMBS”), asset-backed securities (“ABS”), commercial mortgage-backed securities (“CMBS”), U.S. government and agencies (“U.S. government”), state and political subdivisions, and other foreign government, supranational and foreign government-sponsored enterprises (“Other foreign government”). The following tables provide information relating to investments in fixed maturity and equity securities by sector as of December 31, 2017 and 2016 (dollars in thousands): December 31, 2017: Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value % of Total Other-than- temporary impairments in AOCI Available-for-sale: Corporate $ 21,966,803 $ 1,299,594 $ 55,429 $ 23,210,968 60.9 % $ — Canadian government 2,843,273 1,378,510 1,707 4,220,076 11.1 — RMBS 1,695,126 36,632 11,878 1,719,880 4.5 — ABS 1,634,758 18,798 5,194 1,648,362 4.3 275 CMBS 1,285,594 22,627 4,834 1,303,387 3.4 — U.S. government 1,953,436 12,089 21,933 1,943,592 5.1 — State and political subdivisions 647,727 59,997 4,296 703,428 1.8 — Other foreign government 3,254,695 154,507 8,075 3,401,127 8.9 — Total fixed maturity securities $ 35,281,412 $ 2,982,754 $ 113,346 $ 38,150,820 100.0 % $ 275 Non-redeemable preferred stock $ 41,553 $ 479 $ 2,226 $ 39,806 39.7 % Other equity securities 61,288 479 1,421 60,346 60.3 Total equity securities $ 102,841 $ 958 $ 3,647 $ 100,152 100.0 % December 31, 2016: Amortized Unrealized Unrealized Estimated % of Total Other-than- Available-for-sale: Corporate $ 18,924,711 $ 911,618 $ 217,245 $ 19,619,084 61.1 % $ — Canadian government 2,561,605 1,085,982 3,541 3,644,046 11.4 — RMBS 1,258,039 33,917 13,380 1,278,576 4.0 (375 ) ABS 1,443,822 9,350 23,828 1,429,344 4.5 275 CMBS 1,342,440 28,973 7,759 1,363,654 4.2 — U.S. government 1,518,702 12,644 63,044 1,468,302 4.6 — State and political subdivisions 566,761 37,499 12,464 591,796 1.8 — Other foreign government 2,595,707 123,054 19,938 2,698,823 8.4 — Total fixed maturity securities $ 30,211,787 $ 2,243,037 $ 361,199 $ 32,093,625 100.0 % $ (100 ) Non-redeemable preferred stock $ 55,812 $ 1,648 $ 6,337 $ 51,123 18.6 % Other equity securities 229,767 1,792 7,321 224,238 81.4 Total equity securities $ 285,579 $ 3,440 $ 13,658 $ 275,361 100.0 % The Company enters into various collateral arrangements with counterparties that require both the pledging and acceptance of fixed maturity securities as collateral. Pledged fixed maturity securities are included in fixed maturity securities, available-for-sale in the consolidated balance sheets. Fixed maturity securities received as collateral are held in separate custodial accounts and are not recorded on the Company’s consolidated balance sheets. Subject to certain constraints, the Company is permitted by contract to sell or repledge collateral it receives; however, as of December 31, 2017 and 2016 , none of the collateral received had been sold or repledged. The Company also holds assets in trust to satisfy collateral requirements under derivative transactions and certain third-party reinsurance treaties. The following table includes fixed maturity securities pledged and received as collateral and assets in trust held to satisfy collateral requirements under derivative transactions and certain third-party reinsurance treaties as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Fixed maturity securities pledged as collateral $ 72,542 $ 75,622 $ 207,066 $ 210,676 Fixed maturity securities received as collateral n/a 590,417 n/a 300,925 Assets in trust held to satisfy collateral requirements 15,584,296 16,715,281 12,135,258 12,874,370 The Company monitors its concentrations of financial instruments on an ongoing basis, and mitigates credit risk by maintaining a diversified investment portfolio which limits exposure to any one issuer. The Company’s exposure to concentrations of credit risk from single issuers greater than 10% of the Company’s stockholders’ equity included securities of the U.S. government and its agencies, as well as the securities disclosed below, as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Fixed maturity securities guaranteed or issued by: Canadian province of Quebec $ 1,119,337 $ 1,917,996 $ 1,004,261 $ 1,612,957 Canadian province of Ontario 939,837 1,282,944 832,764 1,126,433 The amortized cost and estimated fair value of fixed maturity securities available-for-sale at December 31, 2017 are shown by contractual maturity in the table below (dollars in thousands). Actual maturities can differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Asset and mortgage-backed securities are shown separately in the table below, as they are not due at a single maturity date. Amortized Cost Estimated Fair Value Available-for-sale: Due in one year or less $ 864,993 $ 868,802 Due after one year through five years 7,988,167 8,234,097 Due after five years through ten years 9,286,543 9,781,323 Due after ten years 12,526,231 14,594,969 Asset and mortgage-backed securities 4,615,478 4,671,629 Total $ 35,281,412 $ 38,150,820 Corporate Fixed Maturity Securities The tables below show the major industry types of the Company’s corporate fixed maturity holdings as of December 31, 2017 and 2016 (dollars in thousands): December 31, 2017: Amortized Cost Estimated Fair Value % of Total Finance $ 7,977,885 $ 8,362,774 36.1 % Industrial 11,535,166 12,199,333 52.5 Utility 2,453,752 2,648,861 11.4 Total $ 21,966,803 $ 23,210,968 100.0 % December 31, 2016: Amortized Cost Estimated Fair Value % of Total Finance $ 6,725,199 $ 6,888,968 35.2 % Industrial 10,228,813 10,639,613 54.2 Utility 1,970,699 2,090,503 10.6 Total $ 18,924,711 $ 19,619,084 100.0 % Other-Than-Temporary Impairments—Fixed Maturity and Equity Securities As discussed in Note 2 – “Summary of Significant Accounting Policies,” a portion of certain other-than-temporary impairment (“OTTI”) losses on fixed maturity securities is recognized in AOCI. For these securities, the net amount recognized in the consolidated statements of income (“credit loss impairments”) represents the difference between the amortized cost of the security and the net present value of its projected future cash flows discounted at the effective interest rate implicit in the debt security prior to impairment. Any remaining difference between the fair value and amortized cost is recognized in AOCI. The following table sets forth the amount of pre-tax credit loss impairments on fixed maturity securities held by the Company as of the dates indicated, for which a portion of the OTTI loss was recognized in AOCI, and the corresponding changes in such amounts (dollars in thousands): 2017 2016 2015 Balance, beginning of period $ 6,013 $ 7,284 $ 7,284 Additional impairments - credit loss OTTI recognized on securities previously impaired — 231 — Credit loss impairments previously recognized on securities impaired to fair value during the period (2,336 ) — — Credit loss previously recognized on securities which matured, paid down, prepaid or were sold during the period — (1,502 ) — Balance, end of period $ 3,677 $ 6,013 $ 7,284 Unrealized Losses for Fixed Maturity and Equity Securities Available-for-Sale The following table presents the total gross unrealized losses for the 1,116 and 1,535 fixed maturity and equity securities at December 31, 2017 and 2016 , respectively, where the estimated fair value had declined and remained below amortized cost by the indicated amount (dollars in thousands): 2017 2016 Gross Unrealized Losses % of Total Gross Unrealized Losses % of Total Less than 20% $ 113,466 97.0 % $ 337,831 90.1 % 20% or more for less than six months 689 0.6 19,438 5.2 20% or more for six months or greater 2,838 2.4 17,588 4.7 Total $ 116,993 100.0 % $ 374,857 100.0 % The Company’s determination of whether a decline in value is other-than-temporary includes analysis of the underlying credit and the extent and duration of a decline in value. The Company’s credit analysis of an investment includes determining whether the issuer is current on its contractual payments, evaluating whether it is probable that the Company will be able to collect all amounts due according to the contractual terms of the security and analyzing the overall ability of the Company to recover the amortized cost of the investment. In the Company’s impairment review process, the duration and severity of an unrealized loss position for equity securities are given greater weight and consideration given the lack of contractual cash flows or deferability features. The following tables present the estimated fair values and gross unrealized losses, including other-than-temporary impairment losses reported in AOCI, for 1,116 and 1,535 fixed maturity and equity securities that have estimated fair values below amortized cost as of December 31, 2017 and 2016 , respectively. These investments are presented by class and grade of security, as well as the length of time the related fair value has remained below amortized cost (dollars in thousands): Less than 12 months 12 months or greater Total December 31, 2017: Estimated Fair Value Gross Unrealized Losses Estimated Gross Estimated Gross Investment grade securities: Corporate $ 1,886,212 $ 17,099 $ 1,009,750 $ 28,080 $ 2,895,962 $ 45,179 Canadian government 18,688 91 111,560 1,596 130,248 1,687 RMBS 566,699 5,852 224,439 6,004 791,138 11,856 ABS 434,274 2,707 168,524 2,434 602,798 5,141 CMBS 220,401 1,914 103,269 2,920 323,670 4,834 U.S. government 800,298 6,177 767,197 15,756 1,567,495 21,933 State and political subdivisions 43,510 242 68,666 4,054 112,176 4,296 Other foreign government 369,717 2,707 191,265 4,704 560,982 7,411 Total investment grade securities 4,339,799 36,789 2,644,670 65,548 6,984,469 102,337 Below investment grade securities: Corporate 194,879 3,317 75,731 6,933 270,610 10,250 Canadian government 1,995 20 — — 1,995 20 RMBS — — 1,369 22 1,369 22 ABS — — 1,489 53 1,489 53 Other foreign government 28,600 113 15,134 551 43,734 664 Total below investment grade securities 225,474 3,450 93,723 7,559 319,197 11,009 Total fixed maturity securities $ 4,565,273 $ 40,239 $ 2,738,393 $ 73,107 $ 7,303,666 $ 113,346 Non-redeemable preferred stock $ 82 $ 1 $ 26,471 $ 2,225 $ 26,553 $ 2,226 Other equity securities 5,820 1,023 47,251 398 53,071 1,421 Total equity securities $ 5,902 $ 1,024 $ 73,722 $ 2,623 $ 79,624 $ 3,647 Less than 12 months 12 months or greater Total December 31, 2016: Estimated Gross Estimated Gross Estimated Gross Investment grade securities: Corporate $ 4,661,706 $ 124,444 $ 549,273 $ 43,282 $ 5,210,979 $ 167,726 Canadian government 101,578 3,541 — — 101,578 3,541 RMBS 490,473 9,733 112,216 3,635 602,689 13,368 ABS 563,259 12,010 257,166 9,653 820,425 21,663 CMBS 368,465 6,858 10,853 166 379,318 7,024 U.S. government 1,056,101 63,044 — — 1,056,101 63,044 State and political subdivisions 187,194 9,396 13,635 3,068 200,829 12,464 Other foreign government 524,236 13,372 51,097 2,981 575,333 16,353 Total investment grade securities 7,953,012 242,398 994,240 62,785 8,947,252 305,183 Below investment grade securities: Corporate 330,757 7,914 163,152 41,605 493,909 49,519 RMBS — — 412 12 412 12 ABS 5,904 700 12,581 1,465 18,485 2,165 CMBS 5,815 735 — — 5,815 735 Other foreign government 32,355 1,258 39,763 2,327 72,118 3,585 Total below investment grade securities 374,831 10,607 215,908 45,409 590,739 56,016 Total fixed maturity securities $ 8,327,843 $ 253,005 $ 1,210,148 $ 108,194 $ 9,537,991 $ 361,199 Non-redeemable preferred stock $ 10,831 $ 831 $ 21,879 $ 5,506 $ 32,710 $ 6,337 Other equity securities 202,068 7,020 6,751 301 208,819 7,321 Total equity securities $ 212,899 $ 7,851 $ 28,630 $ 5,807 $ 241,529 $ 13,658 The Company has no intention to sell, nor does it expect to be required to sell, the securities outlined in the table above, as of the dates indicated. However, unforeseen facts and circumstances may cause the Company to sell fixed maturity and equity securities in the ordinary course of managing its portfolio to meet certain diversification, credit quality and liquidity guidelines. Unrealized losses on below investment grade securities as of December 31, 2017 are primarily related to high-yield corporate securities. Changes in unrealized losses are primarily driven by changes in credit spreads and interest rates. Investment Income, Net of Related Expenses Major categories of investment income, net of related expenses consist of the following (dollars in thousands): 2017 2016 2015 Fixed maturity securities $ 1,401,585 $ 1,285,406 $ 1,177,706 Mortgage loans on real estate 197,755 168,582 149,564 Policy loans 60,617 63,837 62,955 Funds withheld at interest 457,774 368,728 343,031 Short-term investments and cash and cash equivalents 7,171 8,051 7,574 Other 110,460 89,371 61,709 Investment income 2,235,362 1,983,975 1,802,539 Investment expense (80,711 ) (72,089 ) (68,044 ) Investment income, net of related expenses $ 2,154,651 $ 1,911,886 $ 1,734,495 Investment Related Gains (Losses), Net Investment related gains (losses), net, consist of the following (dollars in thousands): 2017 2016 2015 Fixed maturity and equity securities: Other-than-temporary impairment losses on fixed maturities $ (42,639 ) $ (38,805 ) $ (57,380 ) Portion of loss recognized in accumulated other comprehensive income — 74 — Net other-than-temporary impairment losses on fixed maturity securities recognized in earnings $ (42,639 ) $ (38,731 ) $ (57,380 ) Impairment losses on equity securities (1,202 ) — — Gain on investment activity 110,569 154,370 73,079 Loss on investment activity (41,679 ) (49,965 ) (71,893 ) Other impairment losses and change in mortgage loan provision (9,497 ) (11,006 ) (6,953 ) Derivatives and other, net 152,328 39,527 (101,603 ) Total investment related gains (losses), net $ 167,880 $ 94,195 $ (164,750 ) The other-than-temporary impairment losses on fixed maturity securities for 2017, 2016 and 2015 are primarily due to emerging market and high-yield debt exposures. The fluctuations in investment related gains (losses) for derivatives and other are primarily due to changes in the fair value of embedded derivatives related to modified coinsurance and funds withheld treaties, as a result of changes in interest rates, driven primarily by credit spreads. At December 31, 2017 and 2016 the Company held non-income producing securities with amortized costs of $38.8 million and $35.4 million , and estimated fair values of $39.3 million and $47.3 million , respectively. Generally, securities are non-income producing when principal or interest is not paid primarily as a result of bankruptcies or credit defaults, but also include securities where amortization has been discontinued. During 2017, 2016 and 2015 the Company sold fixed maturity and equity securities with fair values of $2,727.8 million , $1,181.6 million , and $1,523.6 million , which were below amortized cost, at gross realized losses of $41.7 million , $50.0 million and $71.9 million , respectively. The Company generally does not engage in short-term buying and selling of securities. Securities Borrowing, Lending and Repurchase Agreements The following table includes the amount of borrowed securities, securities lent and securities collateral received as part of the securities lending program, repurchased/reverse repurchased securities pledged and received and cash received as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Borrowed securities $ 358,875 $ 377,820 $ 263,820 $ 279,186 Securities lending: Securities loaned 117,246 121,551 74,389 73,625 Securities received n/a 128,000 n/a 80,000 Repurchase program/reverse repurchase program: Securities pledged 413,819 428,344 476,531 499,891 Securities received n/a 417,550 n/a 515,200 The Company also held cash collateral for securities lending and the repurchase program/reverse repurchase programs of $31.2 million and $28.8 million at December 31, 2017 and 2016 , respectively. No cash or securities have been pledged by the Company for its securities borrowing program as of December 31, 2017 and 2016 . The following tables present information on the Company’s securities lending and repurchase transactions as of December 31, 2017 and 2016 , respectively (dollars in thousands). Collateral associated with certain borrowed securities is not included within the tables as the collateral pledged to each counterparty is the right to reinsurance treaty cash flows. December 31, 2017 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total Securities lending transaction: Corporate $ — $ — $ — $ 121,551 $ 121,551 Total — — — 121,551 121,551 Repurchase transactions: Corporate — — 312 184,334 184,646 RMBS — — — — — U.S. government — — — 220,765 220,765 Foreign government — — — 21,802 21,802 Other 1,131 — — — 1,131 Total 1,131 — 312 426,901 428,344 Total transactions $ 1,131 $ — $ 312 $ 548,452 $ 549,895 Gross amount of recognized liabilities for securities lending and repurchase transactions in preceding table $ 576,786 Amounts related to agreements not included in offsetting disclosure $ 26,891 December 31, 2016 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total Securities lending transaction: Corporate $ — $ — $ 4,017 $ 69,608 $ 73,625 Total — — 4,017 69,608 73,625 Repurchase transactions: Corporate $ — $ — $ 3,220 $ 166,979 $ 170,199 RMBS — — — 92,546 92,546 U.S. government — — — 216,000 216,000 Foreign government — — — 19,900 19,900 Other 1,246 — — — 1,246 Total 1,246 — 3,220 495,425 499,891 Total transactions $ 1,246 $ — $ 7,237 $ 565,033 $ 573,516 Gross amount of recognized liabilities for repurchase transactions in preceding table $ 624,032 Amounts related to agreements not included in offsetting disclosure $ 50,516 The Company has elected to offset amounts recognized as receivables and payables resulting from the repurchase/reverse repurchase programs. After the effect of offsetting, the net amount presented on the consolidated balance sheets was a liability of $1.1 million and $5.5 million as of December 31, 2017 and 2016 , respectively. As of December 31, 2017 and 2016 , the Company recognized payables resulting from cash received as collateral associated with a repurchase agreement as discussed above. Amounts owed to and due from the counterparties may be settled in cash or offset, in accordance with the agreements. Mortgage Loans on Real Estate Mortgage loans represented approximately 8.5% and 8.4% of the Company’s total investments as of December 31, 2017 and 2016 , respectively. As of December 31, 2017 , mortgage loans were geographically dispersed throughout the U.S. with the largest concentrations in California ( 19.5% ), Texas ( 8.4% ) and Georgia ( 7.6% ) and include loans secured by properties in Canada ( 2.3% ). The recorded investment in mortgage loans on real estate presented below is gross of unamortized deferred loan origination fees and expenses, and valuation allowances. The distribution of mortgage loans by property type is as follows as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Carrying Value Percentage of Total Carrying Value Percentage of Total Property type: Office building $ 1,487,392 33.6 % $ 1,270,113 33.6 % Retail 1,270,676 28.8 1,179,936 31.2 Industrial 938,612 21.3 713,461 18.8 Apartment 510,052 11.6 447,088 11.8 Other commercial 206,439 4.7 172,609 4.6 Recorded investment 4,413,171 100.0 % $ 3,783,207 100.0 % Unamortized balance of loan origination fees and expenses (3,254 ) — Valuation allowances (9,384 ) (7,685 ) Total mortgage loans on real estate $ 4,400,533 $ 3,775,522 The maturities of the mortgage loans as of December 31, 2017 and 2016 are as follows (dollars in thousands): 2017 2016 Recorded Investment % of Total Recorded Investment % of Total Due within five years $ 1,091,066 24.8 % $ 822,073 21.7 % Due after five years through ten years 2,516,872 57.0 2,099,559 55.5 Due after ten years 805,233 18.2 861,575 22.8 Total $ 4,413,171 100.0 % $ 3,783,207 100.0 % The following tables set forth certain key credit quality indicators of the Company’s recorded investment in mortgage loans as of December 31, 2017 and 2016 (dollars in thousands): Recorded Investment Debt Service Ratios Construction loans >1.20x 1.00x - 1.20x <1.00x Total % of Total December 31, 2017: Loan-to-Value Ratio 0% - 59.99% $ 2,148,428 $ 53,979 $ 3,801 $ — $ 2,206,208 50.0 % 60% - 69.99% 1,517,029 47,128 43,921 — 1,608,078 36.4 70% - 79.99% 396,446 19,461 15,367 — 431,274 9.8 Greater than 80% 120,850 30,713 6,362 9,686 167,611 3.8 Total $ 4,182,753 $ 151,281 $ 69,451 $ 9,686 $ 4,413,171 100.0 % Recorded Investment Debt Service Ratios >1.20x 1.00x - 1.20x <1.00x Total % of Total December 31, 2016: Loan-to-Value Ratio 0% - 59.99% $ 1,859,640 $ 64,749 $ 1,366 $ 1,925,755 50.8 % 60% - 69.99% 1,257,788 34,678 — 1,292,466 34.2 70% - 79.99% 370,092 20,869 24,369 415,330 11.0 Greater than 80% 114,297 — 35,359 149,656 4.0 Total $ 3,601,817 $ 120,296 $ 61,094 $ 3,783,207 100.0 % The age analysis of the Company’s past due recorded investments in mortgage loans as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 31-60 days past due $ 17,100 $ — 61-90 days past due 2,056 — Total past due 19,156 — Current 4,394,015 3,783,207 Total $ 4,413,171 $ 3,783,207 The following table presents the recorded investment in mortgage loans, by method of measuring impairment, and the related valuation allowances, as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Mortgage loans: Individually measured for impairment $ 5,858 $ 2,216 Collectively measured for impairment 4,407,313 3,780,991 Recorded investment 4,413,171 3,783,207 Valuation allowances: Individually measured for impairment — — Collectively measured for impairment 9,384 7,685 Total valuation allowances 9,384 7,685 Information regarding the Company’s loan valuation allowances for mortgage loans as of December 31, 2017, 2016 and 2015 are as follows (dollars in thousands): 2017 2016 2015 Balance, beginning of period $ 7,685 $ 6,813 $ 6,471 Provision 1,691 872 342 Translation adjustment 8 — — Balance, end of period $ 9,384 $ 7,685 $ 6,813 Information regarding the portion of the Company’s mortgage loans that were impaired as of December 31, 2017 and 2016 is as follows (dollars in thousands): Unpaid Principal Balance Recorded Investment Related Allowance Carrying Value December 31, 2017: Impaired mortgage loans with no valuation allowance recorded $ 6,427 $ 5,858 $ — $ 5,858 Impaired mortgage loans with valuation allowance recorded — — — — Total impaired mortgage loans $ 6,427 $ 5,858 $ — $ 5,858 December 31, 2016: Impaired mortgage loans with no valuation allowance recorded $ 2,758 $ 2,216 $ — $ 2,216 Impaired mortgage loans with valuation allowance recorded — — — — Total impaired mortgage loans $ 2,758 $ 2,216 $ — $ 2,216 The Company’s average investment balance of impaired mortgage loans and the related interest income are reflected in the table below for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): 2017 2016 2015 Average Investment (1) Interest Income Average Investment (1) Interest Income Average Investment (1) Interest Income Impaired mortgage loans with no valuation allowance recorded $ 3,621 $ 186 $ 2,249 $ 142 $ 6,033 $ 330 Impaired mortgage loans with valuation allowance recorded — — — — 11,592 770 Total $ 3,621 $ 186 $ 2,249 $ 142 $ 17,625 $ 1,100 (1) Average recorded investment represents the average loan balances as of the beginning of period and all subsequent quarterly end of period balances. The Company did not acquire any impaired mortgage loans during the years ended December 31, 2017 and 2016 . The Company had no mortgage loans that were on a nonaccrual status at December 31, 2017 and 2016 . Policy Loans Policy loans comprised approximately 2.6% and 3.2% of the Company’s total investments as of December 31, 2017 and 2016 , respectively, the majority of which are associated with one client. These policy loans present no credit risk because the amount of the loan cannot exceed the obligation due to the ceding company upon the death of the insured or surrender of the underlying policy. The provisions of the treaties in force and the underlying policies determine the policy loan interest rates. The Company earns a spread between the interest rate earned on policy loans and the interest rate credited to corresponding liabilities. Funds Withheld at Interest Funds withheld at interest comprised approximately 11.8% and 13.1% of the Company’s total investments as of December 31, 2017 and 2016 , respectively. Of the $6.1 billion funds withheld at interest balance, net of embedded derivatives, as of December 31, 2017 , $4.1 billion of the balance is associated with one client. For reinsurance agreements written on a modified coinsurance basis and certain agreements written on a coinsurance funds withheld basis, assets equal to the net statutory reserves are withheld and legally owned and managed by the ceding company and are reflected as funds withheld at interest on the Company’s consolidated balance sheets. In the event of a ceding company’s insolvency, the Company would need to assert a claim on the assets supporting its reserve liabilities. However, the risk of loss to the Company is mitigated by its ability to offset amounts it owes the ceding company for claims or allowances against amounts owed to the Company from the ceding company. Other Invested Assets Other invested assets include equity securities, limited partnership interests, joint ventures (other than operating joint ventures), derivative contracts, and FVO contractholder-directed unit-linked investments. Other invested assets also include Federal Home Loan Bank of Des Moines (“FHLB”) common stock, equity release mortgages and structured loans, all of which are included in other in the table below. Other invested assets represented approximately 3.1% and 3.6% of the Company’s total investments as of December 31, 2017 and 2016 , respectively. Carrying values of these assets as of December 31, 2017 and 2016 are as follows (dollars in thousands): 2017 2016 Equity securities $ 100,152 $ 275,361 Limited partnerships and real estate joint ventures 781,124 687,522 Derivatives 137,613 229,108 FVO contractholder-directed unit-linked investments 218,541 190,120 Other 368,054 209,829 Total other invested assets $ 1,605,484 $ 1,591,940

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	DERIVATIVE INSTRUMENTS Derivatives, except for embedded derivatives and longevity and mortality swaps, are carried on the Company’s consolidated balance sheets in other invested assets or other liabilities, at fair value. Longevity and mortality swaps are included on the consolidated balance sheets in other assets or other liabilities, at fair value. Embedded derivative assets and liabilities on modified coinsurance or funds withheld arrangements are included on the consolidated balance sheets with the host contract in funds withheld at interest, at fair value. Embedded derivative liabilities on indexed annuity and variable annuity products are included on the consolidated balance sheets with the host contract in interest-sensitive contract liabilities, at fair value. The following table presents the notional amounts and gross fair value of derivative instruments prior to taking into account the netting effects of master netting agreements as of December 31, 2017 and 2016 (dollars in thousands): December 31, 2017 December 31, 2016 Notional Carrying Value/Fair Value Notional Carrying Value/Fair Value Amount Assets Liabilities Amount Assets Liabilities Derivatives not designated as hedging instruments: Interest rate swaps $ 996,204 $ 59,809 $ 2,372 $ 949,556 $ 78,405 $ 5,949 Financial futures 412,438 — — 475,968 — — Foreign currency forwards 6,030 — 28 25,000 — 5,070 Consumer price index swaps 221,932 — 2,160 20,615 — 262 Credit default swaps 961,200 8,319 1,651 926,000 12,012 2,871 Equity options 632,251 23,271 — 525,894 33,459 — Longevity swaps 960,400 40,659 — 841,360 26,958 — Mortality swaps — — 1,683 50,000 — 2,462 Synthetic guaranteed investment contracts 10,052,576 — — 8,834,700 — — Embedded derivatives in: Modified coinsurance or funds withheld arrangements — 122,194 — — — 22,529 Indexed annuity products — — 861,758 — — 805,672 Variable annuity products — — 152,470 — — 184,636 Total non-hedging derivatives 14,243,031 254,252 1,022,122 12,649,093 150,834 1,029,451 Derivatives designated as hedging instruments: Interest rate swaps 435,000 — 20,389 435,000 27,901 31,223 Foreign currency swaps 672,921 65,207 8,496 928,505 104,359 734 Foreign currency forwards 553,175 1,265 7,720 — — — Total hedging derivatives 1,661,096 66,472 36,605 1,363,505 132,260 31,957 Total derivatives $ 15,904,127 $ 320,724 $ 1,058,727 $ 14,012,598 $ 283,094 $ 1,061,408 Netting Arrangements Certain of the Company’s derivatives are subject to enforceable master netting arrangements and reported as a net asset or liability in the consolidated balance sheets. The Company nets all derivatives that are subject to such arrangements. The Company has elected to include all derivatives, except embedded derivatives, in the tables below, irrespective of whether they are subject to an enforceable master netting arrangement or a similar agreement. See Note 4 – “Investments” for information regarding the Company’s securities borrowing, lending, repurchase and repurchase/reverse repurchase programs. See “Embedded Derivatives” below for information regarding the Company’s bifurcated embedded derivatives. The following table provides information relating to the Company’s derivative instruments as of December 31, 2017 and December 31, 2016 (dollars in thousands): Gross Amounts Not Offset in the Balance Sheet Gross Amounts Recognized Gross Amounts Offset in the Balance Sheet Net Amounts Presented in the Balance Sheet Financial Instruments (1) Cash Collateral Pledged/ Received Net Amount December 31, 2017: Derivative assets $ 198,530 $ (20,258 ) $ 178,272 $ (862 ) $ (185,900 ) $ (8,490 ) Derivative liabilities 44,499 (20,258 ) 24,241 (58,156 ) (22,221 ) (56,136 ) December 31, 2016: Derivative assets $ 283,094 $ (27,028 ) $ 256,066 $ (16,913 ) $ (254,498 ) $ (15,345 ) Derivative liabilities 48,571 (27,028 ) 21,543 (95,863 ) (1,441 ) (75,761 ) (1) Includes initial margin posted to a central clearing partner. Accounting for Derivative Instruments and Hedging Activities The Company does not enter into derivative instruments for speculative purposes. As discussed below under “Non-qualifying Derivatives and Derivatives for Purposes Other Than Hedging,” the Company uses various derivative instruments for risk management purposes that either do not qualify or have not been qualified for hedge accounting treatment. As of December 31, 2017 and 2016 , the Company held interest rate swaps that were designated and qualified as cash flow hedges of interest rate risk, for variable rate liabilities and foreign currency assets, foreign currency swaps and foreign currency forwards that were designated and qualified as hedges of a portion of its net investment in its foreign operations, foreign currency swaps that were designated and qualified as fair value hedges of foreign currency risk, and derivative instruments that were not designated as hedging instruments. See Note 2 – “Summary of Significant Accounting Policies” for a detailed discussion of the accounting treatment for derivative instruments, including embedded derivatives. Derivative instruments are carried at fair value and generally require an insignificant amount of cash at inception of the contracts. Fair Value Hedges The Company designates and reports certain foreign currency swaps to hedge the foreign currency fair value exposure of foreign currency denominated assets as fair value hedges when they meet the requirements of the general accounting principles for Derivatives and Hedging. The gain or loss on the hedged item attributable to a change in foreign currency and the offsetting gain or loss on the related foreign currency swaps as of December 31, 2017, 2016 and 2015 were (dollars in thousands): Type of Fair Value Hedge Hedged Item Gains (Losses) Recognized for Derivatives Gains (Losses) Recognized for Hedged Items Ineffectiveness Recognized in Investment Related Gains (Losses) For the Year Ended December 31, 2017: Foreign currency swaps Foreign-denominated fixed maturity securities $ 9,456 $ (9,456 ) $ — For the Year Ended December 31, 2016: Foreign currency swaps Foreign-denominated fixed maturity securities $ (1,700 ) $ 1,700 $ — For the Year Ended December 31, 2015: Foreign currency swaps Foreign-denominated fixed maturity securities $ 4,008 $ (4,008 ) $ — A regression analysis was used, both at inception of the hedge and on an ongoing basis, to determine whether each derivative used in a hedged transaction is highly effective in offsetting changes in the hedged item. For the foreign currency swaps, the change in fair value related to changes in the benchmark interest rate and credit spreads are excluded from the hedge effectiveness. For the years ended December 31, 2017, 2016 and 2015 , $2.0 million , $0.4 million and $0.8 million , respectively, of the change in the estimated fair value of derivatives, was excluded from hedge effectiveness. Cash Flow Hedges Certain derivative instruments are designated as cash flow hedges when they meet the requirements of the general accounting principles for Derivatives and Hedging . The Company designates and accounts for the following as cash flows: (i) certain interest rate swaps, in which the cash flows of liabilities are variable based on a benchmark rate; (ii) certain interest rate swaps, in which the cash flows of assets are denominated in different currencies, commonly referred to as cross-currency swaps; and (iii) forward bond purchase commitments. The following table presents the components of AOCI, before income tax, and the consolidated income statement classification where the gain or loss is recognized related to cash flow hedges for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): Amounts Included in AOCI Balance December 31, 2014 $ (31,591 ) Gains (losses) deferred in other comprehensive income (loss) on the effective portion of cash flow hedges 2,676 Amounts reclassified to investment related (gains) losses, net 87 Amounts reclassified to investment income (569 ) Balance December 31, 2015 (29,397 ) Gains (losses) deferred in other comprehensive income (loss) on the effective portion of cash flow hedges 27,110 Amounts reclassified to investment related (gains) losses, net 278 Amounts reclassified to investment income (487 ) Balance December 31, 2016 (2,496 ) Gains (losses) deferred in other comprehensive income (loss) on the effective portion of cash flow hedges 6,316 Amounts reclassified to investment related (gains) losses, net (775 ) Amounts reclassified to investment income (505 ) Amounts reclassified to interest expense 79 Balance December 31, 2017 $ 2,619 As of December 31, 2017 , the before-tax deferred net gains (losses) on derivative instruments recorded in AOCI that are expected to be reclassified to earnings during the next twelve months are approximately $0.7 million and $(0.8) million in investment income and interest expense, respectively. The following table presents the effective portion of derivatives in cash flow hedging relationships on the consolidated statements of income and the consolidated statements of stockholders’ equity for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): Effective Portion Derivative Type Gains (Losses) Deferred in OCI Gains (Losses) Reclassified into Income from OCI For the year ended December 31, 2017: Investment Related Gains (Losses) Investment Income Interest Expense Interest rate $ (5,649 ) $ — $ — $ (79 ) Currency/Interest rate 11,955 — 380 — Forward bond purchase commitments 10 775 125 — Total $ 6,316 $ 775 $ 505 $ (79 ) For the year ended December 31, 2016: Interest rate $ 27,901 $ — $ — $ — Currency/Interest rate (791 ) — 510 — Forward bond purchase commitments — (278 ) (23 ) — Total $ 27,110 $ (278 ) $ 487 $ — For the year ended December 31, 2015: Currency/Interest rate $ (11,422 ) $ — $ 343 $ — Forward bond purchase commitments 14,098 (87 ) 226 — Total $ 2,676 $ (87 ) $ 569 $ — All components of each derivative’s gain or loss were included in the assessment of hedge effectiveness. For the years ended December 31, 2017, 2016 and 2015 , the ineffective portion of derivatives reported as cash flow hedges was not material to the Company’s results of operations. Also, there were no material amounts reclassified into earnings relating to instances in which the Company discontinued cash flow hedge accounting because the forecasted transaction did not occur by the anticipated date or within the additional time period permitted by the authoritative guidance for the accounting for derivatives and hedging. Hedges of Net Investments in Foreign Operations The Company uses foreign currency swaps and foreign currency forwards to hedge a portion of its net investment in certain foreign operations against adverse movements in exchange rates. The following table illustrates the Company’s net investments in foreign operations (“NIFO”) hedges for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): Derivative Gains (Losses) Deferred in AOCI For the year ended Type of NIFO Hedge (1) (2) 2017 2016 2015 Foreign currency swaps $ (37,567 ) $ (10,234 ) $ 96,019 Foreign currency forwards (10,386 ) — — (1) There were no sales or substantial liquidations of net investments in foreign operations that would have required the reclassification of gains or losses from accumulated other comprehensive income (loss) into investment income during the periods presented. (2) There was no ineffectiveness recognized for the Company’s hedges of net investments in foreign operations. The cumulative foreign currency translation gain recorded in AOCI related to these hedges was $113.7 million and $161.6 million at December 31, 2017 and 2016 , respectively. If a hedged foreign operation was sold or substantially liquidated, the amounts in AOCI would be reclassified to the consolidated statements of income. A pro rata portion would be reclassified upon partial sale of a hedged foreign operation. Non-qualifying Derivatives and Derivatives for Purposes Other Than Hedging The Company uses various other derivative instruments for risk management purposes that either do not qualify or have not been qualified for hedge accounting treatment. The gain or loss related to the change in fair value for these derivative instruments is recognized in investment related gains (losses), net in the consolidated statements of income, except where otherwise noted. A summary of the effect of non-hedging derivatives, including embedded derivatives, on the Company’s consolidated statements of income for the years ended December 31, 2017, 2016 and 2015 is as follows (dollars in thousands): Gains (Losses) for the Years Ended December 31, Type of Non-hedging Derivative Income Statement Location of Gains (Losses) 2017 2016 2015 Interest rate swaps Investment related gains (losses), net $ 11,278 $ 7,649 $ 20,358 Interest rate options Investment related gains (losses), net — — 3,275 Financial futures Investment related gains (losses), net (36,160 ) (40,242 ) 319 Foreign currency forwards Investment related gains (losses), net 591 1,630 (1,160 ) Consumer price index swaps Investment related gains (losses), net (2,078 ) (401 ) (208 ) Credit default swaps Investment related gains (losses), net 18,118 18,100 (4,683 ) Equity options Investment related gains (losses), net (42,953 ) (28,270 ) (16,899 ) Longevity swaps Other revenues 9,358 13,095 8,228 Mortality swaps Other revenues (921 ) (172 ) (1,822 ) Subtotal (42,767 ) (28,611 ) 7,408 Embedded derivatives in: Modified coinsurance or funds withheld arrangements Investment related gains (losses), net 144,723 54,169 (98,792 ) Indexed annuity products Interest credited (80,062 ) 10,708 19,440 Variable annuity products Investment related gains (losses), net 32,166 7,835 (33,192 ) Total non-hedging derivatives $ 54,060 $ 44,101 $ (105,136 ) Types of Derivatives Used by the Company Interest Rate Swaps Interest rate swaps are used by the Company primarily to reduce market risks from changes in interest rates, to alter interest rate exposure arising from mismatches between assets and liabilities (duration mismatches) and to manage the risk of cash flows of liabilities that are variable based on a benchmark rate. With an interest rate swap, the Company agrees with another party to exchange, at specified intervals, the difference between two rates, which can be either fixed-rate or floating-rate interest amounts, tied to an agreed-upon notional principal amount. These transactions are executed pursuant to master agreements that provide for a single net payment or individual gross payments at each due date. The Company utilizes interest rate swaps in cash flow and non-qualifying hedging relationships. Interest Rate Options Interest rate options, commonly referred to as swaptions, have been used by the Company primarily to hedge living benefit guarantees embedded in certain variable annuity products. A swaption, used to hedge against adverse changes in interest rates, is an option to enter into a swap with a forward starting effective date. The Company pays an upfront premium for the right to exercise this option in the future. Financial Futures Exchange-traded equity futures are used primarily to economically hedge liabilities embedded in certain variable annuity products. With exchange-traded equity futures transactions, the Company agrees to purchase or sell a specified number of contracts, the value of which is determined by the relevant stock indices, and to post variation margin on a daily basis in an amount equal to the difference between the daily estimated fair values of those contracts. The Company enters into exchange-traded equity futures with regulated futures commission merchants that are members of the exchange. Equity Options Equity index options are used by the Company primarily to hedge minimum guarantees embedded in certain variable annuity products. To hedge against adverse changes in equity indices volatility, the Company buys put options. The contracts are net settled in cash based on differentials in the indices at the time of exercise and the strike price. Equity warrants have also been used by the Company to economically hedge the variability in anticipated cash flows for the acquisition of investment securities. Consumer Price Index Swaps Consumer price index (“CPI”) swaps are used by the Company primarily to economically hedge liabilities embedded in certain insurance products where value is directly affected by changes in a designated benchmark consumer price index. With a CPI swap transaction, the Company agrees with another party to exchange the actual amount of inflation realized over a specified period of time for a fixed amount of inflation determined at inception. These transactions are executed pursuant to master agreements that provide for a single net payment or individual gross payments to be made by the counterparty at each due date. Most of these swaps will require a single payment to be made by one counterparty at the maturity date of the swap. Foreign Currency Swaps Foreign currency swaps are used by the Company to reduce the risk from fluctuations in foreign currency exchange rates associated with its assets and liabilities denominated in foreign currencies. With a foreign currency swap transaction, the Company agrees with another party to exchange, at specified intervals, the difference between one currency and another at a forward exchange rate calculated by reference to an agreed upon principal amount. The principal amount of each currency is exchanged at the termination of the currency swap by each party. The Company uses foreign currency swaps in hedges of net investments in foreign operations, fair value hedges and non-qualifying hedge relationships. Foreign Currency Forwards Foreign currency forwards are used by the Company to reduce the risk from fluctuations in foreign currency exchange rates associated with its assets and liabilities denominated in foreign currencies. With a foreign currency forward transaction, the Company agrees with another party to deliver a specified amount of an identified currency at a specified future date. The price is agreed upon at the time of the contract and payment for such a contract is made in a different currency at the specified future date. The Company uses foreign currency forwards in hedges of net investments in foreign operations and non-qualifying hedge relationships. Forward Bond Purchase Commitments Forward bond purchase commitments are used by the Company to hedge against the variability in the anticipated cash flows required to purchase securities. With forward bond purchase commitments, the forward price is agreed upon at the time of the contract and payment for such contract is made at the future specified settlement date of the securities. Credit Default Swaps The Company sells protection under single name credit default swaps and credit default swap index tranches to diversify its credit risk exposure in certain portfolios and, in combination with purchasing securities, to replicate characteristics of similar investments based on the credit quality and term of the credit default swap. Credit default triggers for indexed reference entities and single name reference entities are defined in the contracts. The Company’s maximum exposure to credit loss equals the notional value for credit default swaps. In the event of default of a referencing entity, the Company is typically required to pay the protection holder the full notional value less a recovery amount determined at auction. The following table presents the estimated fair value, maximum amount of future payments and weighted average years to maturity of credit default swaps sold by the Company at December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Rating Agency Designation of Referenced Credit Obligations (1) Estimated Fair Value of Credit Default Swaps Maximum Amount of Future Payments under Credit Default Swaps (2) Weighted Average Years to Maturity (3) Estimated Fair Maximum (2) Weighted (3) AAA/AA+/AA/AA-/A+/A/A- Single name credit default swaps $ 3,128 $ 162,000 2.9 $ 1,726 $ 150,500 3.8 Subtotal 3,128 162,000 2.9 1,726 150,500 3.8 BBB+/BBB/BBB- Single name credit default swaps 4,469 361,700 2.9 1,426 347,200 3.7 Credit default swaps referencing indices (55 ) 422,600 4.0 6,295 416,000 5.0 Subtotal 4,414 784,300 3.5 7,721 763,200 4.4 BB+/BB/BB- Single name credit default swaps 30 5,000 1.5 (477 ) 9,000 3.5 Subtotal 30 5,000 1.5 (477 ) 9,000 3.5 Total $ 7,572 $ 951,300 3.4 $ 8,970 $ 922,700 4.3 (1) The rating agency designations are based on ratings from Standard and Poor’s (“S&P”). (2) Assumes the value of the referenced credit obligations is zero. (3) The weighted average years to maturity of the credit default swaps is calculated based on weighted average notional amounts. The Company also purchases credit default swaps to reduce its risk against a drop in bond prices due to credit concerns of certain bond issuers. If a credit event, as defined by the contract, occurs, the Company is able to put the bond back to the counterparty at par. Longevity Swaps The Company enters into longevity swaps in the form of out-of-the-money options, which provide protection against changes in mortality improvement to retirement plans and insurers of such plans. With a longevity swap transaction, the Company agrees with another party to exchange a proportion of a notional value. The proportion is determined by the difference between a predefined benefit, and the realized benefit plus the future expected benefit, calculated by reference to a population index for a fixed premium. Mortality Swaps Mortality swaps have been used by the Company to hedge risk from changes in mortality experience associated with its reinsurance of life insurance risk. The Company agrees with another party to exchange, at specified intervals, a proportion of a notional value determined by the difference between a predefined expected and realized claim amount on a designated index of reinsured lives, for a fixed percentage (premium) each term. The mortality swaps matured in 2017 and an accrued liability for amounts owed to the counterparty is recorded in other liabilities at December 31, 2017. Synthetic Guaranteed Investment Contracts The Company sells fee-based synthetic guaranteed investment contracts to retirement plans which include investment-only, stable value contracts. The assets are owned by the trustees of such plans, who invest the assets under the terms of investment guidelines to which the Company agrees. The contracts contain a guarantee of a minimum rate of return on participant balances supported by the underlying assets, and a guarantee of liquidity to meet certain participant-initiated plan cash flow requirements. These contracts are reported as derivatives and recorded at fair value. Embedded Derivatives The Company has certain embedded derivatives which are required to be separated from their host contracts and reported as derivatives. Host contracts include reinsurance treaties structured on a modified coinsurance or funds withheld basis. Additionally, the Company reinsures equity-indexed annuity and variable annuity contracts with benefits that are considered embedded derivatives, including guaranteed minimum withdrawal benefits, guaranteed minimum accumulation benefits, and guaranteed minimum income benefits. The changes in fair values of embedded derivatives on equity-indexed annuities described below relate to changes in the fair value associated with capital market and other related assumptions. The Company’s utilization of a credit valuation adjustment did not have a material effect on the change in fair value of its embedded derivatives for the years ended December 31, 2017, 2016 and 2015 . The related gains (losses) and the effect on net income after amortization of DAC and income taxes for the years ended December 31, 2017, 2016 and 2015 are reflected in the following table (dollars in thousands): 2017 2016 2015 Embedded derivatives in modified coinsurance or funds withheld arrangements included in investment related gains $ 144,723 $ 54,169 $ 98,792 After the associated amortization of DAC and taxes, the related amounts included in net income 48,316 9,160 (26,025 ) Embedded derivatives in variable annuity contracts included in investment related gains 32,166 7,835 (33,192 ) After the associated amortization of DAC and taxes, the related amounts included in net income 53,645 (41,201 ) (29,008 ) Amounts related to embedded derivatives in equity-indexed annuities included in benefits and expenses (80,062 ) 10,708 19,440 After the associated amortization of DAC and taxes, the related amounts included in net income (68,808 ) (4,148 ) 6,204 Credit Risk The Company manages its credit risk related to over-the-counter (“OTC”) derivatives by entering into transactions with creditworthy counterparties, maintaining collateral arrangements and through the use of master netting agreements that provide for a single net payment to be made by one counterparty to another at each due date and upon termination. The credit exposure of the Company’s OTC derivative transactions is represented by the contracts with a positive fair value (market value) at the reporting date. To reduce credit exposures, the Company seeks to (i) enter into OTC derivative transactions pursuant to master netting agreements that provide for a netting of payments and receipts with a single counterparty and (ii) enter into agreements that allow the use of credit support annexes, which are bilateral rating-sensitive agreements that require collateral postings at established threshold levels. Certain of the Company’s OTC derivatives are cleared derivatives, which are bilateral transactions between the Company and a counterparty where the transactions are cleared through a clearinghouse, such that each derivative counterparty is only exposed to the default of the clearinghouse. These cleared transactions require initial and daily variation margin collateral postings and include certain interest rate swaps and credit default swaps entered into on or after June 10, 2013, related to guidelines implemented under the Dodd-Frank Wall Street Reform and Consumer Protection Act. In 2017, the Company followed the Chicago Mercantile Exchange amended rulebook to legally characterize variation margin payments as settlements of the derivative’s mark-to-market exposure and not collateral. Also, the Company enters into exchange-traded futures through regulated exchanges and these transactions are settled on a daily basis, thereby reducing credit risk exposure in the event of non-performance by counterparties to such financial instruments. The Company enters into various collateral arrangements, which require both the posting and accepting of collateral in connection with its derivative instruments. Collateral agreements contain attachment thresholds that may vary depending on the posting party’s ratings. Additionally, a decline in the Company’s or the counterparty’s credit ratings to specified levels could result in potential settlement of the derivative positions under the Company’s agreements with its counterparties. The Company also has exchange-traded futures, which require the maintenance of a margin account. As exchange-traded futures are affected through regulated exchanges, and positions are marked to market on a daily basis, the Company has minimal exposure to credit-related losses in the event of nonperformance by counterparties. The Company’s credit exposure related to derivative contracts is generally limited to the fair value at the reporting date plus or minus any collateral posted or held by the Company. Information regarding the Company’s credit exposure related to its over-the-counter derivative contracts, centrally cleared derivative contracts and margin account for exchange-traded futures at December 31, 2017 and 2016 is reflected in the following table (dollars in thousands): 2017 2016 Estimated fair value of derivatives in net asset position $ 155,714 $ 236,985 Cash provided as collateral (1) 22,221 1,441 Securities pledged to counterparties as collateral (2) 58,156 95,863 Cash pledged from counterparties as collateral (3) (185,900 ) (254,498 ) Securities pledged from counterparties as collateral (4) (862 ) (16,913 ) Initial margin for cleared derivatives (58,156 ) (73,571 ) Net amount after application of master netting agreements and collateral $ (8,827 ) $ (10,693 ) Margin account related to exchange-traded futures (5) $ 6,538 $ 9,687 (1) Consists of receivable from counterparty, included in other assets. (2) Included in available-for-sale securities, primarily consists of U.S. Treasury and government agency securities. (3) Included in cash and cash equivalents, with obligation to return cash collateral recorded in other liabilities. (4) Consists of U.S. Treasury and government agency securities. (5) Included in other assets.

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities	FAIR VALUE OF ASSETS AND LIABILITIES Fair Value Measurement General accounting principles for Fair Value Measurements and Disclosures define fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. These principles also establish a fair value hierarchy which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value and describes three levels of inputs that may be used to measure fair value: Level 1 - Unadjusted quoted prices in active markets for identical assets or liabilities. Active markets are defined as having the following characteristics for the measured asset/liability: (i) many transactions, (ii) current prices, (iii) price quotes not varying substantially among market makers, (iv) narrow bid/ask spreads and (v) most information publicly available. The Company’s Level 1 assets and liabilities are traded in active exchange markets. Level 2 - Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or market standard valuation techniques and assumptions that use significant inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Such observable inputs include benchmarking prices for similar assets in active, liquid markets, quoted prices in markets that are not active and observable yields and spreads in the market. The Company’s Level 2 assets and liabilities include investment securities with quoted prices that are traded less frequently than exchange-traded instruments and derivative contracts whose values are determined using market standard valuation techniques. Level 2 valuations are generally obtained from third party pricing services for identical or comparable assets or liabilities or through the use of valuation methodologies using observable market inputs. Prices from servicers are validated through analytical reviews and assessment of current market activity. Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the related assets or liabilities. Level 3 assets and liabilities include those whose value is determined using market standard valuation techniques described above. When observable inputs are not available, the market standard techniques for determining the estimated fair value of certain securities that trade infrequently, and therefore have little transparency, rely on inputs that are significant to the estimated fair value and that are not observable in the market or cannot be derived principally from or corroborated by observable market data. These unobservable inputs can be based in large part on management judgment or estimation and cannot be supported by reference to market activity. Even though unobservable, management believes these inputs are based on assumptions deemed appropriate given the circumstances and consistent with what other market participants would use when pricing similar assets and liabilities. Prices are determined using valuation methodologies such as discounted cash flow models and other similar techniques that require management’s judgment or estimation in developing inputs that are consistent with those other market participants would use when pricing similar assets and liabilities. Non-binding broker quotes, which are utilized when pricing service information is not available, are reviewed for reasonableness based on the Company’s understanding of the market, and are generally considered Level 3. Under certain circumstances, based on its observations of transactions in active markets, the Company may conclude the prices received from independent third party pricing services or brokers are not reasonable or reflective of market activity. In those instances, the Company would apply internally developed valuation techniques to the related assets or liabilities. Additionally, the Company’s embedded derivatives, all of which are associated with reinsurance treaties, and longevity and mortality swaps are classified in Level 3 since their values include significant unobservable inputs. When inputs used to measure the fair value of an asset or liability fall within different levels of the hierarchy, the level within which the fair value measurement is categorized is based on the lowest level input that is significant to the fair value measurement in its entirety, except for fair value measurements using NAV. For example, a Level 3 fair value measurement may include inputs that are observable (Levels 1 and 2) and unobservable (Level 3). Therefore, gains and losses for such assets and liabilities categorized within Level 3 may include changes in fair value that are attributable to both observable inputs (Levels 1 and 2) and unobservable inputs (Level 3). Assets and Liabilities by Hierarchy Level Assets and liabilities measured at fair value on a recurring basis as of December 31, 2017 and December 31, 2016 are summarized below (dollars in thousands): December 31, 2017: Fair Value Measurements Using: Total Level 1 Level 2 Level 3 Assets: Fixed maturity securities – available-for-sale: Corporate $ 23,210,968 $ — $ 21,873,696 $ 1,337,272 Canadian government 4,220,076 — 3,626,134 593,942 RMBS 1,719,880 — 1,611,998 107,882 ABS 1,648,362 — 1,524,888 123,474 CMBS 1,303,387 — 1,300,153 3,234 U.S. government 1,943,592 1,818,006 103,075 22,511 State and political subdivisions 703,428 — 662,225 41,203 Other foreign government 3,401,127 — 3,396,035 5,092 Total fixed maturity securities – available-for-sale 38,150,820 1,818,006 34,098,204 2,234,610 Funds withheld at interest – embedded derivatives 122,194 — — 122,194 Cash equivalents 356,788 354,071 2,717 — Short-term investments 50,746 — 47,650 3,096 Other invested assets: Non-redeemable preferred stock 39,806 39,806 — — Other equity securities 60,346 60,346 — — Derivatives: Interest rate swaps 51,359 — 51,359 — Foreign currency forwards 730 — 730 — CPI swaps (221 ) — (221 ) — Credit default swaps 5,908 — 5,908 — Equity options 16,932 — 16,932 — Foreign currency swaps 62,905 — 62,905 — FVO contractholder-directed unit-linked investments 218,541 217,618 923 — Total other invested assets 456,306 317,770 138,536 — Other assets - longevity swaps 40,659 — — 40,659 Total $ 39,177,513 $ 2,489,847 $ 34,287,107 $ 2,400,559 Liabilities: Interest sensitive contract liabilities – embedded derivatives $ 1,014,228 $ — $ — $ 1,014,228 Other liabilities: Derivatives: Interest rate swaps 14,311 — 14,311 — Foreign currency forwards 7,213 — 7,213 — CPI swaps 1,939 — 1,939 — Credit default swaps (760 ) — (760 ) — Equity options (6,339 ) — (6,339 ) — Foreign currency swaps 6,194 — 6,194 — Mortality swaps 1,683 — — 1,683 Total $ 1,038,469 $ — $ 22,558 $ 1,015,911 December 31, 2016: Fair Value Measurements Using: Total Level 1 Level 2 Level 3 Assets: Fixed maturity securities – available-for-sale: Corporate $ 19,619,084 $ 310,995 $ 18,035,836 $ 1,272,253 Canadian government 3,644,046 — 3,168,081 475,965 RMBS 1,278,576 — 1,118,285 160,291 ABS 1,429,344 — 1,210,064 219,280 CMBS 1,363,654 — 1,342,509 21,145 U.S. government 1,468,302 1,345,755 98,059 24,488 State and political subdivisions 591,796 — 550,130 41,666 Other foreign government 2,698,823 276,729 2,409,225 12,869 Total fixed maturity securities – available-for-sale 32,093,625 1,933,479 27,932,189 2,227,957 Funds withheld at interest – embedded derivatives (22,529 ) — — (22,529 ) Cash equivalents 338,601 338,601 — — Short-term investments 44,241 8,276 32,619 3,346 Other invested assets: Non-redeemable preferred stock 51,123 38,317 12,806 — Other equity securities 224,238 224,238 — — Derivatives: Interest rate swaps 93,508 — 93,508 — Credit default swaps 9,136 — 9,136 — Equity options 26,070 — 26,070 — Foreign currency swaps 100,394 — 100,394 — FVO contractholder-directed unit-linked investments 190,120 188,891 1,229 — Other 11,036 11,036 — — Total other invested assets 705,625 462,482 243,143 — Other assets - longevity swaps 26,958 — — 26,958 Total $ 33,186,521 $ 2,742,838 $ 28,207,951 $ 2,235,732 Liabilities: Interest sensitive contract liabilities – embedded derivatives $ 990,308 $ — $ — $ 990,308 Other liabilities: Derivatives: Interest rate swaps 24,374 — 24,374 — Foreign currency forwards 5,070 — 5,070 — CPI swaps 262 — 262 — Credit default swaps (5 ) — (5 ) — Equity options (7,389 ) — (7,389 ) — Foreign currency swaps (3,231 ) — (3,231 ) — Mortality swaps 2,462 — — 2,462 Total $ 1,011,851 $ — $ 19,081 $ 992,770 The Company may utilize information from third parties, such as pricing services and brokers, to assist in determining the fair value for certain assets and liabilities; however, management is ultimately responsible for all fair values presented in the Company’s financial statements. This includes responsibility for monitoring the fair value process, ensuring objective and reliable valuation practices and pricing of assets and liabilities, and approving changes to valuation methodologies and pricing sources. The selection of the valuation technique(s) to apply considers the definition of an exit price and the nature of the asset or liability being valued and significant expertise and judgment is required. The Company performs initial and ongoing analysis and review of the various techniques utilized in determining fair value to ensure that they are appropriate and consistently applied, and that the various assumptions are reasonable. The Company analyzes and reviews the information and prices received from third parties to ensure that the prices represent a reasonable estimate of the fair value and to monitor controls around pricing, which includes quantitative and qualitative analysis and is overseen by the Company’s investment and accounting personnel. Examples of procedures performed include, but are not limited to, review of pricing trends, comparison of a sample of executed prices of securities sold to the fair value estimates, comparison of fair value estimates to management’s knowledge of the current market, and ongoing confirmation that third party pricing services use, wherever possible, market-based parameters for valuation. In addition, the Company utilizes both internal and external cash flow models to analyze the reasonableness of fair values utilizing credit spread and other market assumptions, where appropriate. As a result of the analysis, if the Company determines there is a more appropriate fair value based upon the available market data, the price received from the third party is adjusted accordingly. The Company also determines if the inputs used in estimated fair values received from pricing services are observable by assessing whether these inputs can be corroborated by observable market data. For assets and liabilities reported at fair value, the Company utilizes when available, fair values based on quoted prices in active markets that are regularly and readily obtainable. Generally, these are very liquid investments and the valuation does not require management judgment. When quoted prices in active markets are not available, fair value is based on market valuation techniques, market comparable pricing and the income approach. The use of different techniques, assumptions and inputs may have a material effect on the estimated fair values of the Company’s securities holdings. For the periods presented, the application of market standard valuation techniques applied to similar assets and liabilities has been consistent. The methods and assumptions the Company uses to estimate the fair value of assets and liabilities measured at fair value on a recurring basis are summarized below. Fixed Maturity Securities – The fair values of the Company’s publicly-traded fixed maturity securities are generally based on prices obtained from independent pricing services. Prices from pricing services are sourced from multiple vendors, and a vendor hierarchy is maintained by asset type based on historical pricing experience and vendor expertise. The Company generally receives prices from multiple pricing services for each security, but ultimately uses the price from the vendor that is highest in the hierarchy for the respective asset type. To validate reasonableness, prices are periodically reviewed as explained above. Consistent with the fair value hierarchy described above, securities with quotes from pricing services are generally reflected within Level 2, as they are primarily based on observable pricing for similar assets and/or other market observable inputs. If the pricing information received from third party pricing services is not reflective of market activity or other inputs observable in the market, the Company may challenge the price through a formal process with the pricing service. If the Company ultimately concludes that pricing information received from the independent pricing service is not reflective of fair value, non-binding broker quotes are used, if available. If the Company concludes that the values from both pricing services and brokers are not reflective of fair value an internally developed valuation may be prepared; however, this occurs infrequently. Internally developed valuations or non-binding broker quotes are also used to determine fair value in circumstances where vendor pricing is not available. These valuations may use significant unobservable inputs, which reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset. Observable market data may not be available in certain circumstances such as market illiquidity and credit events related to the security. Pricing service overrides, internally developed valuations and non-binding broker quotes are generally based on significant unobservable inputs and are reflected as Level 3 in the valuation hierarchy. The inputs used in the valuation of corporate and government securities include, but are not limited to standard market observable inputs which are derived from, or corroborated by, market observable data including market yield curve, duration, call provisions, observable prices and spreads for similar publicly traded or privately traded issues that incorporate the credit quality and industry sector of the issuer. For structured securities, valuation is based primarily on matrix pricing or other similar techniques using standard market inputs including spreads for actively traded securities, spreads off benchmark yields, expected prepayment speeds and volumes, current and forecasted loss severity, rating, weighted average coupon, weighted average maturity, average delinquency rates, geographic region, debt-service coverage ratios and issuance-specific information including, but not limited to: collateral type, payment terms of the underlying assets, payment priority within the tranche, structure of the security, deal performance and vintage of loans. When observable inputs are not available, the market standard valuation techniques for determining the estimated fair value of certain types of securities that trade infrequently, and therefore have little or no price transparency, rely on inputs that are significant to the estimated fair value that are not observable in the market or cannot be derived principally from or corroborated by observable market data. These unobservable inputs can be based in large part on management judgment or estimation, and cannot be supported by reference to market activity. Even though unobservable, these inputs are based on assumptions deemed appropriate given the circumstances and are believed to be consistent with what other market participants would use when pricing such securities. The fair values of private placement securities are primarily determined using a discounted cash flow model. In certain cases these models primarily use observable inputs with a discount rate based upon the average of spread surveys collected from private market intermediaries who are active in both primary and secondary transactions, taking into account, among other factors, the credit quality and industry sector of the issuer and the reduced liquidity associated with private placements. Generally, these securities have been reflected within Level 3. For certain private fixed maturities, the discounted cash flow model may also incorporate significant unobservable inputs, which reflect the Company’s own assumptions about the inputs market participants would use in pricing the security. To the extent management determines that such unobservable inputs are not significant to the price of a security, a Level 2 classification is made. Otherwise, a Level 3 classification is used. Embedded Derivatives – The fair value of embedded derivative liabilities, including those calculated by third parties, are monitored through the use of attribution reports to quantify the effect of underlying sources of fair value change, including capital market inputs based on policyholder account values, interest rates and short-term and long-term implied volatilities, from period to period. Actuarial assumptions are based on experience studies performed internally in combination with available industry information and are reviewed on a periodic basis, at least annually. For embedded derivative liabilities associated with the underlying products in reinsurance treaties, primarily equity-indexed and variable annuity treaties, the Company utilizes a discounted cash flow model, which includes an estimate of future equity option purchases and an adjustment for a CVA. The variable annuity embedded derivative calculations are performed by third parties based on methodology and input assumptions provided by the Company. To validate the reasonableness of the resulting fair value, the Company’s internal actuaries perform reviews and analytical procedures on the results. The capital market inputs to the model, such as equity indexes, short-term equity volatility and interest rates, are generally observable. The valuation also requires certain significant inputs, which are generally not observable and accordingly, the valuation is considered Level 3 in the fair value hierarchy, see “Level 3 Measurements and Transfers” below for a description. The fair value of embedded derivatives associated with funds withheld reinsurance treaties is determined based upon a total return swap technique with reference to the fair value of the investments held by the ceding company that support the Company’s funds withheld at interest asset with an adjustment for a CVA. The fair value of the underlying assets is generally based on market observable inputs using industry standard valuation techniques. The valuation also requires certain significant inputs, which are generally not observable and accordingly, the valuation is considered Level 3 in the fair value hierarchy, see “Level 3 Measurements and Transfers” below for a description. Credit Valuation Adjustment – The Company uses a structural default risk model to estimate a CVA. The input assumptions are a combination of externally derived and published values (default threshold and uncertainty), market inputs (interest rate, equity price per share, debt per share, equity price volatility) and insurance industry data (Loss Given Default), adjusted for market recoverability. Cash Equivalents and Short-Term Investments – Cash equivalents and short-term investments include money market instruments, commercial paper and other highly liquid debt instruments. Money market instruments are generally valued using unadjusted quoted prices in active markets that are accessible for identical assets and are primarily classified as Level 1. The fair value of certain other cash equivalents and short-term investments, such as bonds with original maturities less than twelve months, are based upon other market observable data and are typically classified as Level 2. However, certain short-term investments may incorporate significant unobservable inputs resulting in a Level 3 classification. Various time deposits, certificates of deposit and sweeps carried as cash equivalents or short-term investments are not measured at estimated fair value and therefore are excluded from the tables presented. Equity Securities – Equity securities consist principally of exchange-traded funds and preferred stock of publicly and privately traded companies. The fair values of publicly traded equity securities are primarily based on quoted market prices in active markets and are classified within Level 1 in the fair value hierarchy. The fair values of preferred equity securities, for which quoted market prices are not readily available, are based on prices obtained from independent pricing services and these securities are generally classified within Level 2 in the fair value hierarchy. Non-binding broker quotes for equity securities are generally based on significant unobservable inputs and are reflected as Level 3 in the fair value hierarchy. FVO Contractholder-Directed Unit-Linked Investments – FVO contractholder-directed investments supporting unit-linked variable annuity type liabilities primarily consist of exchange-traded funds and, to a lesser extent, fixed maturity securities and cash and cash equivalents. The fair values of the exchange-traded securities are primarily based on quoted market prices in active markets and are classified within Level 1 of the hierarchy. The fair value of the fixed maturity contractholder-directed securities is determined on a basis consistent with the methodologies described above for fixed maturity securities and are classified within Level 2 of the hierarchy. Derivative Assets and Derivative Liabilities – All of the derivative instruments utilized by the Company, except for longevity and mortality swaps, are classified within Level 2 on the fair value hierarchy. These derivatives are principally valued using an income approach. Valuations of interest rate contracts are based on present value techniques, which utilize significant inputs that may include the swap yield curve, London Interbank Offered Rate (“LIBOR”) basis curves, and repurchase rates. Valuations of foreign currency contracts are based on present value techniques, which utilize significant inputs that may include the swap yield curve, LIBOR basis curves, currency spot rates, and cross currency basis curves. Valuations of credit contracts, are based on present value techniques, which utilize significant inputs that may include the swap yield curve, credit curves, and recovery rates. Valuations of equity market contracts, are based on present value techniques, which utilize significant inputs that may include the swap yield curve, spot equity index levels, and dividend yield curves. Valuations of equity market contracts, option-based, are based on option pricing models, which utilize significant inputs that may include the swap yield curve, spot equity index levels, dividend yield curves, and equity volatility. The Company does not currently have derivatives, except for longevity and mortality swaps, included in Level 3 measurement. Longevity and Mortality Swaps – The Company utilizes a discounted cash flow model to estimate the fair value of longevity and mortality swaps. The fair value of these swaps includes an accrual for premiums payable and receivable. Some inputs to the valuation model are generally observable, such as interest rates and actual population mortality experience. The valuation also requires significant inputs that are generally not observable and, accordingly, the valuation is considered Level 3 in the fair value hierarchy. Level 3 Measurements and Transfers As of December 31, 2017 and December 31, 2016 , respectively, the Company classified approximately 5.9% and 6.9% of its fixed maturity securities in the Level 3 category. These securities primarily consist of private placement corporate securities, bank loans, Canadian provincial strips, below investment grade mortgage-backed securities and subprime asset-backed securities with inactive trading markets. The significant unobservable inputs used in the fair value measurement of the Company’s corporate, sovereign, government-backed, and other political subdivision investments are probability of default, liquidity premium and subordination premium. Significant increases (decreases) in any of those inputs in isolation would result in a significantly lower (higher) fair value measurement. Generally, a change in the assumption used for the probability of default is accompanied by a directionally similar change in the assumptions used for the liquidity premium and subordination premium. For securities with a fair value derived using the market comparable pricing valuation technique, liquidity premium is the only significant unobservable input. The significant unobservable inputs used in the fair value measurement of the Company’s asset and mortgage-backed securities are prepayment rates, probability of default, liquidity premium and loss severity in the event of default. Significant increases (decreases) in any of those inputs in isolation would result in a significantly lower (higher) fair value measurement. Generally, a change in the assumption used for the probability of default is accompanied by a directionally similar change in the assumption used for the liquidity premium and loss severity and a directionally opposite change in the assumption used for prepayment rates. The actuarial assumptions used in the fair value of embedded derivatives which include assumptions related to lapses, withdrawals, and mortality, are based on experience studies performed by the Company in combination with available industry information and are reviewed on a periodic basis, at least annually. The significant unobservable inputs used in the fair value measurement of embedded derivatives are assumptions associated with policyholder experience and selected capital market assumptions for equity-indexed and variable annuities. The selected capital market assumptions, which include long-term implied volatilities, are projections based on short-term historical information. Changes in interest rates, equity indices, equity volatility, CVA, and actuarial assumptions regarding policyholder experience may result in significant fluctuations in the value of embedded derivatives. Fair value measurements associated with funds withheld reinsurance treaties are generally not materially sensitive to changes in unobservable inputs associated with policyholder experience. The primary drivers of change in these fair values are related to movements of credit spreads, which are generally observable. Increases (decreases) in market credit spreads tend to decrease (increase) the fair value of embedded derivatives. Increases (decreases) in the CVA assumption tend to decrease (increase) the magnitude of the fair value of embedded derivatives. Fair value measurements associated with variable annuity treaties are sensitive to both capital markets inputs and policyholder experience inputs. Increases (decreases) in lapse rates tend to decrease (increase) the value of the embedded derivatives associated with variable annuity treaties. Increases (decreases) in the long-term volatility assumption tend to increase (decrease) the fair value of embedded derivatives. Increases (decreases) in the CVA assumption tend to decrease (increase) the magnitude of the fair value of embedded derivatives. The actuarial assumptions used in the fair value of longevity and mortality swaps include assumptions related to the level and volatility of mortality. The assumptions are based on studies performed by the Company in combination with available industry information and are reviewed on a periodic basis, at least annually. The following table presents quantitative information about significant unobservable inputs used in Level 3 fair value measurements that are developed internally by the Company as of December 31, 2017 and 2016 (dollars in thousands): Fair Value Valuation Unobservable Range (Weighted Average) Assets: 2017 2016 Technique Input 2017 2016 Corporate $ 173,579 $ 167,815 Market comparable securities Liquidity premium 0-2% (1%) 0-2% (1%) U.S. government 22,511 24,488 Market comparable securities Liquidity premium 0-1% (1%) 0-1% (1%) State and political subdivisions 4,616 4,670 Market comparable securities Liquidity premium 1 % 1 % Funds withheld at interest- embedded derivatives 122,194 (22,529 ) Total return swap Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (8%) Withdrawal 0-5% (3%) 0-5% (3%) CVA 0-5% (1%) 0-5% (1%) Crediting rate 2-4% (2%) 2-4% (2%) Longevity swaps 40,659 26,958 Discounted cash flow Mortality 0-100% (2%) 0-100% (2%) Mortality improvement (10%)-10% (3%) (10%)-10% (3%) Liabilities: Interest sensitive contract liabilities- embedded derivatives- indexed annuities 861,758 805,672 Discounted cash flow Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (8%) Withdrawal 0-5% (3%) 0-5% (3%) Option budget projection 2-4% (2%) 2-4% (2%) Interest sensitive contract liabilities- embedded derivatives- variable annuities 152,470 184,636 Discounted cash flow Mortality 0-100% (1%) 0-100% (2%) Lapse 0-25% (5%) 0-25% (6%) Withdrawal 0-7% (3%) 0-7% (3%) CVA 0-5% (1%) 0-5% (1%) Long-term volatility 0-27% (8%) 0-27% (14%) Mortality swaps 1,683 2,462 Discounted cash flow Mortality 0-100% (1%) 0-100% (1%) The Company recognizes transfers of assets and liabilities into and out of levels within the fair value hierarchy at the beginning of the quarter in which the actual event or change in circumstances that caused the transfer occurs. Transfers between Levels 1 and 2 are made to reflect changes in observability of inputs and market activity. There were no transfers between Level 1 and Level 2 for year ended December 31, 2016. The transfers from level 1 to level 2 during the year ended December 31, 2017 were due to the Company refining its process related to the observability of inputs and market activity. The following tables present the transfers between Level 1 and Level 2 during the year ended December 31, 2017 (dollars in thousands): 2017 Transfers from Level 1 to Level 2 Transfers from Level 2 to Level 1 Fixed maturity securities - available-for-sale: Corporate $ 596,809 $ 88,674 Other foreign government 317,640 — Assets and liabilities transferred into Level 3 are due to a lack of observable market transactions and price information. Certain transfers into Level 3 were also due to ratings downgrades on mortgage-backed securities that previously had investment-grade ratings. Assets and liabilities are transferred out of Level 3 when circumstances change such that significant inputs can be corroborated with market observable data. This may be due to a significant increase in market activity for the asset or liability, a specific event, or one or more significant input(s) becoming observable. Transfers out of Level 3 were primarily the result of the Company obtaining observable pricing information or a third party pricing quotation that appropriately reflects the fair value of those assets and liabilities. In addition, certain transfers out of Level 3 were also due to ratings upgrades on mortgage-backed securities that previously had below investment-grade ratings. The reconciliations for all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) are as follows: For the year ended December 31, 2017: Fixed maturity securities - available-for-sale Corporate Canadian government RMBS ABS Fair value, beginning of period $ 1,272,253 $ 475,965 $ 160,291 $ 219,280 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (1,429 ) 13,180 (346 ) 1,776 Investment related gains (losses), net 4,991 — 729 245 Included in other comprehensive income (6,719 ) 104,797 2,341 7,044 Purchases (1) 408,995 — 76,792 45,215 Sales (1) (89,248 ) — (28,043 ) — Settlements (1) (285,958 ) — (18,988 ) (87,328 ) Transfers into Level 3 47,360 — 9,100 85,152 Transfers out of Level 3 (12,973 ) — (93,994 ) (147,910 ) Fair value, end of period $ 1,337,272 $ 593,942 $ 107,882 $ 123,474 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment i

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2017
Reinsurance Disclosures [Abstract]
Reinsurance	REINSURANCE In the normal course of business, the Company seeks to limit its exposure to loss on any single insured and to recover a portion of benefits paid by ceding reinsurance to other insurance enterprises or reinsurers under excess coverage and coinsurance contracts. In the individual life markets, the Company retains a maximum of $8.0 million of coverage per individual life. Claims in excess of this retention amount are retroceded to retrocessionaires; however, the Company remains fully liable to the ceding company for the entire amount of risk it assumes. In certain limited situations the Company has retained more than $8.0 million per individual policy. The Company enters into agreements with other reinsurers to mitigate the residual risk related to the over-retained policies. Additionally, due to some lower face amount reinsurance coverage provided by the Company in addition to individual life, such as group life, disability and health, under certain circumstances, the Company could potentially incur net claims totaling more than $8.0 million per individual life. Retrocession reinsurance treaties do not relieve the Company from its obligations to direct writing companies. Failure of retrocessionaires to honor their obligations could result in losses to the Company. Consequently, allowances would be established for amounts deemed uncollectible. At December 31, 2017 and 2016 , no allowances were deemed necessary. The Company regularly evaluates the financial condition of the insurance companies from which it assumes and to which it cedes reinsurance. Retrocessions are arranged through the Company’s retrocession pools for amounts in excess of the Company’s retention limit. As of December 31, 2017 and 2016 , all rated retrocession pool participants followed by the A.M. Best Company were rated “A- (excellent)” or better. The Company verifies retrocession pool participants’ ratings on a quarterly basis. For a majority of the retrocessionaires that were not rated, security in the form of letters of credit or trust assets has been posted. In addition, the Company performs annual financial reviews of its retrocessionaires to evaluate financial stability and performance. In addition to its third party retrocessionaires, various RGA reinsurance subsidiaries retrocede amounts in excess of their retention to affiliated subsidiaries. The following table presents information for the Company’s ceded reinsurance receivable assets, including the respective amount and A.M. Best rating for each reinsurer representing in excess of five percent of the total as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Reinsurer A.M. Best Rating Amount % of Total Amount % of Total Reinsurer A A+ $ 301,478 38.6 % $ 240,894 35.2 % Reinsurer B A+ 203,898 26.1 183,881 26.9 Reinsurer C A 67,723 8.7 68,832 10.1 Reinsurer D A++ 40,592 5.2 36,202 5.3 Reinsurer E A+ 40,528 5.2 35,484 5.2 Other reinsurers 127,808 16.2 118,679 17.3 Total $ 782,027 100.0 % $ 683,972 100.0 % Included in the total ceded reinsurance receivables balance were $243.8 million and $242.0 million of claims recoverable, of which $1.9 million and $4.0 million were in excess of 90 days past due, as of December 31, 2017 and 2016 , respectively. The effect of reinsurance on net premiums is as follows (dollars in thousands): Years ended December 31, 2017 2016 2015 Direct $ 61,571 $ 57,562 $ 43,106 Reinsurance assumed 10,642,462 10,049,587 9,371,308 Reinsurance ceded (862,903 ) (858,278 ) (843,673 ) Net premiums $ 9,841,130 $ 9,248,871 $ 8,570,741 The effect of reinsurance on claims and other policy benefits as follows (dollars in thousands): Years ended December 31, 2017 2016 2015 Direct $ 104,447 $ 105,435 $ 82,942 Reinsurance assumed 9,281,590 8,621,647 8,205,308 Reinsurance ceded (867,120 ) (733,707 ) (798,868 ) Net claims and other policy benefits $ 8,518,917 $ 7,993,375 $ 7,489,382 The effect of reinsurance on life insurance in force is shown in the following schedule (dollars in millions): Direct Assumed Ceded Net Assumed/Net % December 31, 2017 $ 1,462 $ 3,297,275 $ 205,529 $ 3,093,208 106.6 % December 31, 2016 1,576 3,062,525 214,727 2,849,374 107.5 December 31, 2015 1,686 2,995,079 222,388 2,774,377 108.0 At December 31, 2017 and 2016 , respectively, the Company provided approximately $16.2 billion and $10.8 billion of financial reinsurance, as measured by pre-tax statutory surplus, risk based capital and other financial reinsurance structures, to other insurance companies under financial reinsurance transactions to assist ceding companies in meeting applicable regulatory requirements. Generally, such financial reinsurance is provided by the Company committing cash or assuming insurance liabilities, which are collateralized by future profits on the reinsured business. The Company earns a fee based on the amount of net outstanding financial reinsurance. Reinsurance agreements, whether facultative or automatic, may provide for recapture rights on the part of the ceding company. Recapture rights permit the ceding company to reassume all or a portion of the risk formerly ceded to the reinsurer after an agreed-upon period of time, generally 10 years, or in some cases due to changes in the financial condition or ratings of the reinsurer. Recapture of business previously ceded does not affect premiums ceded prior to the recapture of such business, but would reduce premiums in subsequent periods. Additionally, some treaties give the ceding company the right to request the Company to place assets in trust for their benefit to support their reserve credits, in the event of a downgrade of the Company’s ratings to specified levels, generally non-investment grade levels, or if minimum levels of financial condition are not maintained. As of December 31, 2017 and 2016 , these treaties had approximately $2,901.1 million and $1,935.0 million , respectively, in statutory reserves. Assets placed in trust continue to be owned by the Company, but their use is restricted based on the terms of the trust agreement. Securities with an amortized cost of $2,214.1 million and $2,372.1 million were held in trust to satisfy collateral requirements for reinsurance business for the benefit of certain RGA subsidiaries at December 31, 2017 and 2016 , respectively. In addition, the Company’s collateral financing operations have asset in trust requirements. See Note 14 – “Collateral Finance and Securitization Notes” for additional information. Securities with an amortized cost of $15,584.3 million and $12,135.3 million , as of December 31, 2017 and 2016 , respectively, were held in trust to satisfy collateral requirements under certain third-party reinsurance treaties. Under certain conditions, RGA may be obligated to move reinsurance from one RGA subsidiary company to another or make payments under the treaty. These conditions include change in control or ratings of the subsidiary, insolvency, nonperformance under a treaty, or loss of reinsurance license of such subsidiary.

Deferred Policy Acquisition Cos

Deferred Policy Acquisition Costs	12 Months Ended
	Dec. 31, 2017
Deferred Policy Acquisition Costs Disclosures [Abstract]
Deferred Policy Acquisition Costs	DEFERRED POLICY ACQUISITION COSTS The following reflects the amounts of policy acquisition costs deferred and amortized (dollars in thousands): Years ended December 31, 2017 2016 2015 Balance, beginning of year $ 3,338,605 $ 3,392,437 $ 3,342,575 Capitalization 348,470 350,233 352,260 Amortization (including interest) (432,474 ) (341,115 ) (288,630 ) Change in value of embedded derivatives (70,392 ) (40,077 ) 58,754 Attributed to unrealized investment gains (losses) (8,220 ) (3,541 ) 17,510 Foreign currency translation 63,835 (19,332 ) (90,032 ) Balance, end of year $ 3,239,824 $ 3,338,605 $ 3,392,437 Some reinsurance agreements involve reimbursing the ceding company for allowances and commissions in excess of first-year premiums. These amounts represent acquisition costs and are capitalized to the extent deemed recoverable from the future premiums and amortized against future profits of the business. This type of agreement presents a risk to the extent that the business lapses faster than originally anticipated, resulting in future profits being insufficient to recover the Company’s investment.

Income Tax

Income Tax	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Tax	INCOME TAX The Tax Cuts and Jobs Act of 2017 (“U.S. Tax Reform”) was signed into law on December 22, 2017. U.S. Tax Reform makes broad and complex changes to the U.S. tax code, including, but not limited to, (1) reducing the U.S. federal corporate tax rate from 35 percent to 21 percent; (2) requiring companies to pay a one-time transition tax on certain unrepatriated earnings of foreign subsidiaries; (3) generally eliminating U.S. federal income taxes on dividends from foreign subsidiaries; (4) eliminating the corporate alternative minimum tax (“AMT”) and changing how existing AMT credits can be realized; (5) creating the base erosion anti-abuse tax (“BEAT”), a new minimum tax; (6) establishing a new provision designed to tax global intangible low-taxed income (“GILTI”), which allows for the possibility of using foreign tax credits and a deduction of up to 50 percent to offset the income tax liability (subject to some limitations); and (7) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017. In connection with the Company’s initial analysis of the impact of U.S. Tax Reform, it recorded a discrete provisional net tax benefit of $1,033.8 million in the period ending December 31, 2017. This estimated net benefit primarily consists of the U.S. federal rate reduction from 35 percent to 21 percent applied to the net deferred tax liability. The Company provisionally estimates there would be no one-time transition tax on unrepatriated earnings of foreign subsidiaries. However, this tax could change based on future clarification of U.S. Tax Reform, as well as due to the Company gathering additional information to more precisely compute the transition tax. Further, as a result of U.S. Tax Reform, the Company established a valuation allowance of $58.9 million related to U.S. foreign tax credit carryforwards. The valuation allowance relates to the Company’s interpretation of the changes in the ability to use existing foreign tax credit carryforwards against future foreign branch profits. The valuation allowance could change based on future interpretation and analysis of U.S. Tax Reform. Because of the complexity of the new GILTI tax rules, the Company is continuing to evaluate this provision of U.S. Tax Reform and the application of Accounting Standards Codification 740 (“ASC 740”). Under U.S. GAAP, the Company is allowed to make an accounting policy choice of either (1) treating taxes due on future U.S. inclusions in taxable income related to the GILTI as a current-period expense when incurred (“the period cost method”) or (2) factoring such amounts into a Company’s measurement of its deferred taxes (“the deferred method”). The Company’s selection of an accounting policy with respect to new GILTI tax rules will depend, in part, on analyzing its global income to determine whether the Company expects to have future U.S. inclusions in taxable income related to GILTI and, if so, what the impact is expected to be. Whether the Company expects to have future U.S. inclusions in taxable income related to GILTI depends on not only its current corporate structure, its intercompany reinsurance business flows and estimated future results of global operations, but also its intent and ability to modify its structure and/or its business, the Company is not yet able to reasonably estimate the effect of this provision of U.S. Tax Reform. Therefore, the Company has not made any adjustments related to potential GILTI tax in its financial statements and has not made a policy decision regarding whether to record deferred taxes on GILTI. The SEC issued Staff Accounting Bulletin 118 (“SAB 118”), which provides guidance on accounting for the tax effects of U.S. Tax Reform. SAB 118 provides a measurement period that should not extend beyond one year from U.S. Tax Reform enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of U.S. Tax Reform for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of U.S. Tax Reform is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of U.S. Tax Reform. The Company calculated a provisional estimate of the impact of U.S. Tax Reform. The actual adjustment may vary from this estimate due to a number of uncertainties and factors, including changes in interpretations and assumptions made by the Company, gathering additional information to more precisely compute the pretax deferred tax items upon which the change in rate was applied, and may change due to future further clarification of the new law regulatory and accounting guidance. The Company is still analyzing U.S. Tax Reform and refining its calculations, which could potentially impact the measurement of recorded tax balances as of December 31, 2017. This provisional amount is based on the best information currently available and may be revised and is subject to change. The provisional impact of the enactment of U.S. Tax Reform is reflected in the tables below. Pre-tax income for the years ended December 31, 2017, 2016 and 2015 consists of the following (dollars in thousands): 2017 2016 2015 Pre-tax income - U.S. $ 870,532 $ 758,496 $ 493,328 Pre-tax income - foreign 272,283 285,450 251,467 Total pre-tax income $ 1,142,815 $ 1,043,946 $ 744,795 The provision for income tax expense for the years ended December 31, 2017, 2016 and 2015 consists of the following (dollars in thousands): 2017 2016 2015 Current income tax expense (benefit): U.S. $ 131,108 $ 1,020 $ 1,588 Foreign 36,830 47,706 92,045 Total current 167,938 48,726 93,633 Deferred income tax expense (benefit): U.S. 159,853 273,928 193,204 U.S. Tax Reform provisional estimate (1,033,755 ) — — Foreign 26,598 19,849 (44,208 ) Total deferred (847,304 ) 293,777 148,996 Total provision for income taxes $ (679,366 ) $ 342,503 $ 242,629 The Company’s effective tax rate differed from the U.S. federal income tax statutory rate of 35% as a result of the following for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): 2017 2016 2015 Tax provision at U.S. statutory rate $ 399,985 $ 365,381 $ 260,678 Increase (decrease) in income taxes resulting from: U.S. Tax Reform provisional estimate (1,033,755 ) — — Foreign tax rate differing from U.S. tax rate (21,867 ) (13,974 ) (9,950 ) Differences in tax basis in foreign jurisdictions (23,324 ) (17,770 ) (32,472 ) Deferred tax valuation allowance 29,458 10,963 19,157 Amounts related to audit contingencies (7,184 ) 111 88 Equity compensation excess benefit (10,532 ) — — Corporate rate changes (6,065 ) — — Subpart F for non-full inclusion companies 1,528 1,783 3,473 Foreign tax Credits (1,681 ) (1,683 ) (1,936 ) Return to provision Adjustments (4,674 ) (1,473 ) 1,482 Other, net (1,255 ) (835 ) 2,109 Total provision for income taxes $ (679,366 ) $ 342,503 $ 242,629 Effective tax rate (59.4 )% 32.8 % 32.6 % Total income taxes for the years ended December 31, 2017, 2016 and 2015 were as follows (dollars in thousands): 2017 2016 2015 Provision for income taxes $ (679,366 ) $ 342,503 $ 242,629 Income tax from OCI and additional paid-in-capital: Net unrealized holding gain (loss) on debt and equity securities recognized for financial reporting purposes 306,849 157,929 (339,889 ) Exercise of stock options — (162 ) (2,963 ) Foreign currency translation (42,153 ) 21,081 16,478 Unrealized pension and post retirement 404 1,772 1,726 Total income taxes provided $ (414,266 ) $ 523,123 $ (82,019 ) The tax effects of temporary differences that give rise to significant portions of the deferred income tax assets and liabilities at December 31, 2017 and 2016 , are presented in the following tables (dollars in thousands): 2017 2016 Deferred income tax assets: Nondeductible accruals $ 80,905 $ 125,879 Differences between tax and financial reporting amounts concerning certain reinsurance transactions 96,043 87,688 Differences in the tax basis of cash and invested assets 557 775 Investment income differences 43,230 35,192 Deferred acquisition costs capitalized for tax 88,531 143,003 Net operating loss carryforward 535,374 325,806 Capital loss and tax credit carryforwards 102,143 101,223 Subtotal 946,783 819,566 Valuation allowance (226,884 ) (133,354 ) Total deferred income tax assets 719,899 686,212 Deferred income tax liabilities: Deferred acquisition costs capitalized for financial reporting 627,378 1,013,642 Differences between tax and financial reporting amounts concerning certain reinsurance transactions 1,547,101 1,773,929 Differences in the tax basis of cash and invested assets 674,569 505,841 Investment income differences 1,858 5,635 Differences in foreign currency translation 33,803 91,067 Prepaid expenses — — Total deferred income tax liabilities 2,884,709 3,390,114 Net deferred income tax liabilities $ 2,164,810 $ 2,703,902 Balance sheet presentation of net deferred income tax liabilities: Included in other assets $ 33,499 $ 66,738 Included in deferred income taxes 2,198,309 2,770,640 Net deferred income tax liabilities $ 2,164,810 $ 2,703,902 As of December 31, 2017 , a valuation allowance against deferred tax assets was approximately $226.9 million . During 2017, a valuation allowance was established on the U.S. Foreign tax credit carryforwards of $65.1 million , RGA Reinsurance Company of Australia Limited’s, (“RGA Australia”) net operating losses of $20.1 million , as well as on the deferred tax assets of other jurisdictions of $3.3 million . Further movement in the valuation allowance includes foreign currency translation and reclassifications with other deferred tax assets of $10.6 million and ($5.6) million , respectively. The other significant components of the valuation allowance relate to a partial valuation allowance on the net operating loss carryforwards in RGA Australia and the foreign tax credit carryforwards in RGA International Reinsurance Company dac (“RGA International”). A valuation allowance also exists against the deferred tax assets of other branches and legal entities most of which there is no history of earnings in recent years. As of December 31, 2016, a valuation allowance for deferred tax assets of approximately $133.4 million was provided on the total deferred tax assets in certain jurisdictions. The valuation allowance is primarily related to numerous branches and legal entities for which there is no history of earnings in recent years. Further there is a partial valuation allowance on RGA South Africa, RGA Australia, and Aurora National net operating losses, as well as RGA International’s foreign tax credit. The Company utilizes valuation allowance when it believes, based on the weight of the available evidence, that it is more likely than not that the deferred income tax asset will not be utilized. The earnings of substantially all of the Company’s foreign subsidiaries have been permanently reinvested in foreign operations. No provision has been made for U.S. tax or foreign withholding taxes that may be applicable upon any repatriation or sale. At December 31, 2017 and 2016 , the financial reporting basis in excess of the tax basis for which no deferred taxes have been recognized was approximately $1,442.9 million and $1,147.2 million , respectively. As U.S. Tax Reform generally eliminates U.S. federal income taxes on dividends from foreign subsidiaries, the Company does not expect to incur material income taxes if these funds are repatriated. During 2017, 2016 and 2015 , the Company received federal and foreign income tax refunds of approximately $11.6 million , $6.9 million and $136.8 million , respectively. The Company made cash income tax payments of approximately $48.7 million , $68.0 million and $178.4 million in 2017, 2016 and 2015 , respectively. At December 31, 2017 and 2016 , the Company recognized gross deferred tax assets associated with net operating losses of approximately $2,715.8 million and $1,353.6 million , respectively. The earliest expiration date for any significant net operating losses is 2029. Net operating losses of $181.2 million , $451.4 million , and $1,557.1 million would expire in 2029, 2030, and 2032, respectively if unutilized. The remaining losses where a valuation allowance has not been established that are subject to expiration are $48.0 million and would expire between 2034 and 2036. These net operating losses, other than the net operating losses for which there is a valuation allowance, are expected to be utilized in the normal course of business during the period allowed for carryforwards and in any event, are not expected to be lost, due to the application of tax planning strategies that management would utilize. At December 31, 2017 and 2016 , the Company also has foreign tax credit carryforwards of $152.0 million and $100.9 million , respectively, in the U.S. and Ireland. During 2017 the Company established a valuation allowance of $65.1 million on the U.S. foreign tax credits and the remaining U.S. foreign tax credits of $57.0 million reduced the uncertain tax liabilities. The Ireland foreign tax credit of $29.9 million has a full valuation allowance. The Company also has AMT carryforwards of $25.9 million and $21.3 million , respectively. As a result of U.S. Tax Reform, the AMT credits are fully refundable if unutilized by 2021. The Company has recorded these credits as deferred tax assets. The Company files income tax returns in the U.S. federal jurisdiction and various state and foreign jurisdictions. The Company is under continuous examination by the Internal Revenue Service and is subject to audit by taxing authorities in other foreign jurisdictions in which the Company has significant business operations. The income tax years under examination vary by jurisdiction. The Company is no longer subject to U.S. federal income tax examinations by tax authorities for years prior to 2014, Canadian tax authorities for years prior to 2013 and with a few exceptions, the Company is no longer subject to state and foreign income tax examinations by tax authorities for years prior to 2012. As of December 31, 2017 , the Company’s total amount of unrecognized tax benefits was $321.2 million and the total amount of unrecognized tax benefits that would affect the effective tax rate, if recognized, was $10.9 million . Management believes there will be no material impact to the Company’s effective tax rate related to unrecognized tax benefits over the next 12 months. A reconciliation of the beginning and ending amount of unrecognized tax benefits for the years ended December 31, 2017, 2016 and 2015 , is as follows (dollars in thousands): Total Unrecognized Tax Benefits 2017 2016 2015 Beginning balance, January 1 $ 297,290 $ 296,213 $ 274,661 Additions for tax positions of prior years 247,596 226,720 26,170 Reductions for tax positions of prior years (246,894 ) (229,719 ) (7,820 ) Additions for tax positions of current year 36,438 4,186 3,396 Settlements with tax authorities (13,206 ) (110 ) (194 ) Ending balance, December 31 $ 321,224 $ 297,290 $ 296,213 The Company recognized interest expense (benefit) associated with uncertain tax positions in 2017, 2016 and 2015 of $(5.0) million , $(8.4) million and $8.2 million , respectively. Additionally, the Company recognized penalties of $0.3 million in 2016. As of December 31, 2017 and 2016 , the Company had $15.1 million and $20.4 million , respectively, of accrued interest related to unrecognized tax benefits. There are no penalties accrued as of December 31, 2017.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS Certain subsidiaries of the Company are sponsors or administrators of both qualified and non-qualified defined benefit pension plans (“Pension Plans”). The largest of these plans is a non-contributory qualified defined benefit pension plan sponsored by RGA Reinsurance that covers U.S. employees. The benefits under the Pension Plans are generally based on years of service and compensation levels. The Company also provides select health care and life insurance benefits for certain retired employees. The health care benefits are provided through a self-insured welfare benefit plan. Employees become eligible for these benefits if they meet minimum age and service requirements. The retiree’s cost for health care benefits varies depending upon the credited years of service. The Company recorded benefits expense of approximately $5.3 million , $6.3 million and $9.1 million in 2017, 2016 and 2015 , respectively, that are related to these postretirement plans. Effective January 1, 2017, employees hired in the U. S. are not eligible for retiree health care benefits. Virtually all retirees, or their beneficiaries, contribute a portion of the total cost of postretirement health benefits. Prepaid benefit costs and accrued benefit liabilities are included in other assets and other liabilities, respectively, in the Company’s consolidated balance sheets. A December 31 measurement date is used for all of the defined benefit and postretirement plans. The status of these plans as of December 31, 2017 and 2016 is summarized below (dollars in thousands): December 31, Pension Benefits Other Benefits 2017 2016 2017 2016 Change in benefit obligation: Benefit obligation at beginning of year $ 161,955 $ 142,239 $ 60,524 $ 63,307 Service cost 10,686 10,319 2,543 2,883 Interest Cost 5,326 4,790 2,118 2,259 Participant contributions — — 354 305 Amendments (1) 159 — — (13,743 ) Actuarial (gains) losses 11,336 9,973 5,510 6,228 Settlement (gains) losses (438 ) 258 — — Settlements (12,907 ) (3,152 ) — — Benefits paid (5,974 ) (3,047 ) (851 ) (715 ) Foreign exchange translations and other adjustments 2,000 575 — — Benefit obligation at end of year $ 172,143 $ 161,955 $ 70,198 $ 60,524 (1) Reflects effect of the amendment to RGA’s U.S. retiree health care benefit plan announced in 2016, effective January 1, 2017 and other administrative amendments to the pension plans. The amounts were recorded in AOCI and will be amortized through prior service cost. December 31, Pension Benefits Other Benefits 2017 2016 2017 2016 Change in plan assets: Fair value of plan assets at beginning of year $ 84,770 $ 68,435 $ — $ — Actual return on plan assets 14,481 6,584 — — Employer contributions 22,866 15,950 497 410 Participant contributions — — 354 305 Disbursement for settlements (12,907 ) (3,152 ) — — Benefits paid and expenses (5,974 ) (3,047 ) (851 ) (715 ) Fair value of plan assets at end of year $ 103,236 $ 84,770 $ — $ — Funded status at end of year $ (68,907 ) $ (77,185 ) $ (70,198 ) $ (60,524 ) December 31, Qualified Plans Non-Qualified Plans (1) Total 2017 2016 2017 2016 2017 2016 Aggregate fair value of plan assets $ 103,236 $ 84,770 $ — $ — $ 103,236 $ 84,770 Aggregate projected benefit obligations 107,072 96,418 65,071 65,537 172,143 161,955 Under funded $ (3,836 ) $ (11,648 ) $ (65,071 ) $ (65,537 ) $ (68,907 ) $ (77,185 ) (1) For non-qualified plans, there are no required funding levels. December 31, Pension Benefits Other Benefits 2017 2016 2017 2016 Amounts recognized in accumulated other comprehensive income: Net actuarial loss $ 40,058 $ 46,119 $ 35,672 $ 32,156 Net prior service cost (credit) 804 703 (11,806 ) (13,121 ) Total $ 40,862 $ 46,822 $ 23,866 $ 19,035 The following table presents information for qualified and non-qualified pension plans with a projected benefit obligation in excess of plan assets as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Projected benefit obligation $ 172,143 $ 161,955 Fair value of plan assets 103,236 84,770 The following table presents information for pension plans with an accumulated benefit obligation in excess of plan assets as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Accumulated benefit obligation $ 169,705 $ 158,580 Fair value of plan assets 103,236 84,770 The components of net periodic benefit cost, included in other operating expenses on the consolidated statements of income, and other changes in plan assets and benefit obligations recognized in other comprehensive income were as follows (dollars in thousands): Pension Benefits Other Benefits 2017 2016 2015 2017 2016 2015 Net periodic benefit cost: Service cost $ 10,686 $ 10,319 $ 9,222 $ 2,543 $ 2,883 $ 4,062 Interest cost 5,326 4,790 5,035 2,118 2,259 2,572 Expected return on plan assets (6,215 ) (5,138 ) (4,897 ) — — — Amortization of prior actuarial losses 4,382 4,323 3,429 1,992 1,827 2,465 Amortization of prior service cost (credit) 344 294 309 (1,315 ) (622 ) — Settlements 4,785 1,026 — — — — Net periodic benefit cost 19,308 15,614 13,098 5,338 6,347 9,099 Other changes in plan assets and benefit obligations recognized in other comprehensive income: Net actuarial (gains) losses 2,633 8,785 5,774 5,507 6,228 (2,729 ) Amortization of actuarial (gains) losses (4,382 ) (4,323 ) (3,429 ) (1,992 ) (1,827 ) (2,465 ) Amortization of prior service cost (credit) (344 ) (294 ) (309 ) 1,315 622 — Settlements (4,785 ) (1,026 ) — — — — Prior service cost (credit) (1) 159 — — — (13,743 ) — Foreign exchange translations and other adjustments 759 707 (1,797 ) — — — Total recognized in other comprehensive income (5,960 ) 3,849 239 4,830 (8,720 ) (5,194 ) Total recognized in net periodic benefit cost and other comprehensive income $ 13,348 $ 19,463 $ 13,337 $ 10,168 $ (2,373 ) $ 3,905 (1) Reflects effect of the amendment to RGA’s U.S. retiree health care benefit plan announced in 2016, effective January 1, 2017 and other administrative amendments to the pension plans. The amounts were recorded in AOCI and will be amortized through prior service cost. During 2018, the Company expects to contribute $14.5 million and $1.2 million to the pension plans and other benefit plans, respectively. The following benefit payments, which reflect expected future service as appropriate, are expected to be paid (dollars in thousands): Pension Benefits Other Benefits 2018 $ 9,315 $ 1,238 2019 9,765 1,495 2020 10,885 1,842 2021 11,102 2,188 2022 13,184 2,521 2023-2027 69,285 18,205 The estimated net loss and prior service cost for the defined benefit pension plans and post-retirement plans that will be amortized from accumulated other comprehensive income into net periodic benefit cost over the next fiscal year are $3.4 million and $1.1 million , respectively. Assumptions Weighted average assumptions used to determine the accumulated benefit obligation and net benefit cost or income were as follows: Pension Benefits Other Benefits 2017 2016 2015 2017 2016 2015 Discount rate used to determine benefit obligation 3.40 % 3.80 % 3.99 % 3.56 % 4.10 % 4.43 % Discount rate used to determine net benefit cost or income 3.81 % 3.95 % 3.77 % 4.10 % 4.43 % 4.05 % Expected long-term rate of return on plan assets 7.35 % 7.35 % 7.35 % — % — % — % Rate of compensation increases 4.16 % 4.08 % 4.08 % — % — % — % The expected rate of return on plan assets is based on anticipated performance of the various asset sectors in which the plan invests, weighted by target allocation percentages. Anticipated future performance is based on long-term historical returns of the plan assets by sector, adjusted for the long-term expectations on the performance of the markets. While the precise expected return derived using this approach may fluctuate from year to year, the policy is to hold this long-term assumption constant as long as it remains within reasonable tolerance from the derived rate. This process is consistent for all plan assets as all the assets are invested in mutual funds. The assumed health care cost trend rates used in measuring the accumulated non-pension post-retirement benefit obligation were as follows: December 31, 2017 2016 Pre-Medicare eligible claims 9% down to 5% in 2024 10% down to 5% in 2024 Medicare eligible claims 9% down to 5% in 2024 10% down to 5% in 2024 Assumed health care cost trend rates may have a significant effect on the amounts reported for health care plans. A one-percentage point change in assumed health care cost trend rates would have the following effects (dollars in thousands): One Percent Increase One Percent Decrease Effect on total of service and interest cost components $ 7,941 $ (7,104 ) Effect on accumulated postretirement benefit obligation $ 447 $ (359 ) Plan Assets Target allocations of U.S. qualified pension plan assets are determined with the objective of maximizing returns and minimizing volatility of net assets through adequate asset diversification and partial liability immunization. Adjustments are made to target allocations based on the Company’s assessment of the effect of economic factors and market conditions. The target allocations for plan assets are 60% equity securities and 40% debt securities as of December 31, 2017 and 2016 . The Company’s plan assets are primarily invested in mutual funds. The mutual funds include holdings of S&P 500 securities, large-cap securities, mid-cap securities, small-cap securities, international securities, corporate debt securities, U.S. and other government securities, mortgage-related securities and cash. Equity and debt securities are exposed to various risks, such as interest rate risk, credit risk and overall market volatility. Due to the level of risk associated with certain investment securities, changes in the values of investment securities will occur and any change would affect the amounts reported in the financial statements. The fair values of the Company’s qualified pension plan assets as of December 31, 2017 and 2016 are summarized below (dollars in thousands): December 31, 2017 Fair Value Measurement Using: Total Level 1 Level 2 Level 3 Mutual Funds (1) $ 103,106 $ 103,106 $ — $ — Cash 130 130 — — Total $ 103,236 $ 103,236 $ — $ — (1) Mutual funds were invested 27% in U.S. equity funds, 36% in U.S. fixed income funds, 22% in non-U.S. equity funds and 15% in other. December 31, 2016 Fair Value Measurement Using: Total Level 1 Level 2 Level 3 Mutual Funds (2) $ 84,671 $ 84,671 $ — $ — Cash 99 99 — — Total $ 84,770 $ 84,770 $ — $ — (2) Mutual funds were invested 28% in U.S. equity funds, 37% in U.S. fixed income funds, 20% in non-U.S. equity funds and 15% in other. As of December 31, 2017 and 2016 , the Company classified all of its qualified pension plan assets in the Level 1 category as quoted prices in active markets are available for these assets. See Note 6 – “Fair Value of Asset and Liabilities” for additional detail on the fair value hierarchy. Savings and Investment Plans Certain subsidiaries of RGA also sponsor savings and investment plans under which a portion of employee contributions are matched. Subsidiary contributions to these plans were $14.2 million , $9.9 million and $9.0 million in 2017, 2016 and 2015 , respectively.

Financial Condition and Net Inc

Financial Condition and Net Income on a Statutory Basis - Significant Subsidiaries	12 Months Ended
	Dec. 31, 2017
Statutory Basis [Abstract]
Financial Condition and Net Income on a Statutory Basis - Significant Subsidiaries	FINANCIAL CONDITION AND NET INCOME ON A STATUTORY BASIS – SIGNIFICANT SUBSIDIARIES The domestic and foreign insurance subsidiaries of RGA prepare their statutory financial statements in conformity with statutory accounting practices prescribed or permitted by the applicable state insurance department or local regulatory authority, which vary materially from statements prepared in accordance with GAAP. Prescribed statutory accounting practices in the U.S. include publications of the National Association of Insurance Commissioners (“NAIC”), as well as state laws, local regulations and general administrative rules. The differences between statutory financial statements and financial statements prepared in accordance with GAAP vary between jurisdictions. The principal differences between GAAP and NAIC are that statutory financial statements do not reflect deferred policy acquisition costs and limit deferred tax assets, life benefit reserves predominately use interest rate and mortality assumptions prescribed by the NAIC and local regulatory agencies, bonds are generally carried at amortized cost and reinsurance assets and liabilities are presented net of reinsurance. Statutory net income, and capital and surplus of the Company’s insurance subsidiaries, determined in accordance with statutory accounting practices prescribed by the applicable state insurance department or local regulatory authority are as follows (dollars in thousands): Statutory Capital & Surplus Statutory Net Income (Loss) 2017 2016 2017 2016 2015 RGA Reinsurance (U.S.) $ 1,584,007 $ 1,521,644 $ 138,359 $ 148,576 $ (23,615 ) Reinsurance Company of Missouri 1,557,453 1,651,274 (183,136 ) 272,038 51,041 RGA Life Reinsurance Company of Canada 1,006,190 915,134 25,971 13,947 113,526 RGA Reinsurance Company (Barbados) Ltd. 1,278,006 957,051 309,346 95,859 113,049 RGA Australia 476,528 370,039 78,497 (7,694 ) (18,128 ) RGA Atlantic Reinsurance Company Ltd. 812,307 596,016 213,511 110,172 132,192 RGA Americas Reinsurance Company, Ltd. (1) 4,833,890 3,752,910 624,145 282,226 264,518 Other reinsurance subsidiaries 2,694,317 2,224,833 65,658 130,289 300,847 (1) In 2017, the Company contributed to RGA Americas Reinsurance Company, Ltd. all of the outstanding shares of its wholly-owned subsidiary, RGA Australia. Periods prior to 2017 have been adjusted to reflect this contribution. Each U.S. domestic insurance subsidiary’s state of domicile imposes minimum risk-based capital (“RBC”) requirements that were developed by the NAIC. The formulas for determining the amount of RBC specify various weighting factors that are applied to financial balances or various levels of activity based on the perceived degree of risk. Regulatory compliance is determined by a ratio of total adjusted capital, as defined by the NAIC, to authorized control level RBC, as defined by the NAIC. Companies below specific trigger points or ratios are classified within certain levels, each of which requires specified corrective action. Each of RGA’s U.S. domestic insurance subsidiaries exceeded the minimum RBC requirements for all periods presented herein. These requirements do not represent a significant constraint for the payment of dividends by RGA’s U.S. domestic insurance companies. The licensing orders of the Company’s special purpose companies stipulate a minimum amount of capital required based on the purpose of the entity and the underlying business. These companies are subject to enhanced oversight by the regulator which includes filing detailed plans of operations before commencing operations or making material changes to existing agreements or entering into new agreements. Each of the Company’s Special Purpose Life Reinsurance Captives (“SPLRC”) exceeded the minimum capital requirements for all periods presented herein. The Company’s foreign insurance subsidiaries prepare financial statements in accordance with local regulatory requirements. The regulatory authorities in these foreign jurisdictions establish some form of minimum regulatory capital and surplus requirements. All of the Company’s foreign insurance subsidiaries have regulatory capital and surplus that exceed the local minimum requirements. These requirements do not represent a significant constraint for the payment of dividends by the Company’s foreign insurance companies. The state of domicile of certain of the Company’s SPLRCs follow prescribed accounting practices differing from NAIC statutory accounting practices (“NAIC SAP”) applicable to their statutory financial statements. Specifically, these prescribed practices require that surplus note interest accrued but not approved for payment be reported as a direct reduction of surplus and an addition to the surplus note balance. Under NAIC SAP, surplus note interest is not to be reported until approved for payment and is reported as a reduction of net investment income in the Summary of Operations. In addition, these prescribed practices allow the SPLRC to reflect letters of credit issued for its benefit as an admitted asset and a direct credit to unassigned surplus. Under NAIC SAP, letters of credit issued on behalf of the reporting company are not reported on the balance sheet. A reconciliation of the Company’s surplus between NAIC SAP and practices prescribed by the state of domicile is shown below (dollars in thousands): December 31, 2017 2016 Prescribed practice – surplus note $ 726,531 $ 574,574 Prescribed practice – letters of credit (960,100 ) (615,100 ) Surplus (deficit) – NAIC SAP $ (233,569 ) $ (40,526 ) Reinsurance Company of Missouri (“RCM”), RGA Reinsurance and Chesterfield Reinsurance Company (“Chesterfield Re”) are subject to Missouri statutory provisions that restrict the payment of dividends. They may not pay dividends in any 12 -month period in excess of the greater of the prior year’s statutory net gain from operations or 10% of statutory capital and surplus at the preceding year-end, without regulatory approval. Aurora National is subject to California statutory provisions that are identical to those imposed by Missouri regarding the ability of Aurora National to pay dividends to RGA Reinsurance. The applicable statutory provisions only permit an insurer to pay a shareholder dividend from unassigned surplus. As of January 1, 2018, RGA Reinsurance could pay maximum dividends, without prior approval, of approximately $158.4 million . Any dividends paid by RGA Reinsurance would be paid to RCM, its parent company, which in turn has restrictions related to its ability to pay dividends to RGA. Chesterfield Re would pay dividends to its immediate parent Chesterfield Financial Holdings LLC, (“Chesterfield Financial”), which would in turn pay dividends to RCM, subject to the terms of the indenture for the embedded value securitization transaction, in which Chesterfield Financial cannot declare or pay any dividends so long as any private placement notes are outstanding. The Missouri Department of Insurance, Financial Institution and Professional Registration, allows RCM to pay a dividend to RGA to the extent RCM received the dividend from its subsidiaries, without limitation related to the level of unassigned surplus. Dividend payments from other subsidiaries are subject to regulations in the jurisdiction of domicile, which are generally based on their earnings and/or capital level. Dividend payments from non-U.S. operations are subject to similar restrictions established by local regulators. The non-U.S. regulatory regimes also commonly limit the dividend payments to the parent to a portion of the prior year’s statutory income, as determined by the local accounting principles. The regulators of the Company’s non-U.S. operations may also limit or prohibit profit repatriations or other transfers of funds to the U.S. if such transfers are deemed to be detrimental to the solvency or financial strength of the non-U.S. operations, or for other reasons. Most of the non-U.S. operating subsidiaries are second tier subsidiaries which are owned by various non-U.S. holding companies. The capital and rating considerations applicable to the first tier subsidiaries may also impact the dividend flow to RGA. There are no regulatory restrictions that limit the payment of dividends by RGA, except those generally applicable to Missouri corporations. Dividends are payable by Missouri corporations only under the circumstances specified in The General and Business Corporation Law of Missouri. RGA would not be permitted to pay common stock dividends if there is any accrued and unpaid interest on its subordinated debentures and its junior subordinated debentures. Furthermore, the ability of RGA to pay dividends is dependent on business conditions, income, cash requirements of the Company, receipt of dividends from its subsidiaries, financial covenant provisions and other relevant factors.

Commitments Contingencies and G

Commitments Contingencies and Guarantees	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	COMMITMENTS, CONTINGENCIES AND GUARANTEES Commitments Funding of Investments The Company’s commitments to fund investments as of December 31, 2017 and 2016 are presented in the following table (dollars in thousands): 2017 2016 Limited partnership interests and joint ventures $ 485,197 $ 332,169 Commercial mortgage loans 40,815 126,248 Bank loans and private placements 60,472 58,318 Equity release mortgages 153,937 130,324 The Company anticipates that the majority of its current commitments will be invested over the next five years; however, these commitments could become due any time at the request of the counterparties. Bank loans and private placements are included in fixed maturity securities available-for-sale. Leases The Company leases office space and furniture and equipment under non-cancelable operating lease agreements, which expire at various dates. Future minimum office space annual rentals under non-cancelable operating leases at December 31, 2017 are as follows (dollars in thousands): Operating Leases 2018 $ 11,157 2019 7,108 2020 4,879 2021 3,076 2022 2,421 Thereafter 9,466 Rent expenses amounted to approximately $15.7 million , $13.7 million and $12.1 million for the years ended December 31, 2017, 2016 and 2015 , respectively. Off-Balance Sheet Arrangements In 2013, the Company executed a series of incentive agreements with the County of St. Louis, Missouri (the “County”). Under these agreements, the Company transferred its newly constructed world headquarters to the County in exchange for taxable industrial revenue bonds (the “bonds”), in a series of bond issuances during 2013 and 2014, with a maximum amount of $150.0 million . As a result, the Company was able to reduce the cost of constructing and operating its world headquarters by reducing certain state and local tax expenditures. The Company simultaneously leased the world headquarters from the County and has an option to purchase the world headquarters for a nominal fee upon tendering the bonds back to the County. The payments due to the Company under the terms of the bonds and the amounts owed by the Company under the terms of the lease agreement qualify for the right of offset under GAAP. As such, neither the bonds nor the lease obligation is recorded on the consolidated balance sheets as an asset or liability, respectively. The world headquarters is recorded as an asset of the Company in “Other assets” on the consolidated balance sheets. Contingencies Litigation The Company is subject to litigation in the normal course of its business. The Company currently has no material litigation. A legal reserve is established when the Company is notified of an arbitration demand or litigation or is notified that an arbitration demand or litigation is imminent, it is probable that the Company will incur a loss as a result and the amount of the probable loss is reasonably capable of being estimated. Other Contingencies The Company indemnifies its directors and officers as provided in its charters and by-laws. Since this indemnity generally is not subject to limitation with respect to duration or amount, the Company does not believe that it is possible to determine the maximum potential amount due under this indemnity in the future. Guarantees Statutory Reserve Support RGA, through wholly-owned subsidiaries, has committed to provide statutory reserve support to third-parties, in exchange for a fee, by funding loans if certain defined events occur. Such statutory reserves are required under the U.S. Valuation of Life Policies Model Regulation (commonly referred to as Regulation XXX for term life insurance policies and Regulation A-XXX for universal life secondary guarantees). The third-parties have recourse to RGA should the subsidiary fail to provide the required funding, however, as of December 31, 2017 , the Company does not believe that it will be required to provide any funding under these commitments as the occurrence of the defined events is considered remote. The following table presents the maximum potential obligation for these commitments as of December 31, 2017 (dollars in millions): Commitment Period Maximum Potential Obligation 2023 $ 500.0 2033 450.0 2034 2,000.0 2035 1,314.2 2036 2,932.0 2037 5,750.0 Other Guarantees RGA has issued guarantees to third parties on behalf of its subsidiaries for the payment of amounts due under certain reinsurance treaties, securities borrowing and repurchase arrangements, financing arrangements and office lease obligations, whereby if a subsidiary fails to meet an obligation, RGA or one of its other subsidiaries will make a payment to fulfill the obligation. In limited circumstances, treaty guarantees are granted to ceding companies in order to provide them additional security, particularly in cases where RGA’s subsidiary is relatively new, unrated, or not of a significant size, relative to the ceding company. Liabilities supported by the treaty guarantees, before consideration for any legally offsetting amounts due from the guaranteed party are reflected on the Company’s consolidated balance sheets in a policy related liability. Potential guaranteed amounts of future payments will vary depending on production levels and underwriting results. Guarantees related to securities borrowing and repurchase arrangements provide additional security to third parties should a subsidiary fail to provide securities when due. RGA’s guarantees issued as of December 31, 2017 and 2016 are reflected in the following table (dollars in thousands): 2017 2016 Treaty guarantees $ 1,047,449 $ 902,216 Treaty guarantees, net of assets in trust 926,393 780,786 Securities borrowing and repurchase arrangements 294,325 263,820 Financing arrangements 86,183 119,073 Lease obligations 1,662 2,428

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	DEBT Long-Term Debt The Company’s long-term debt consists of the following as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 $300 million 5.625% Senior Notes due 2017 $ — $ 299,945 $400 million 6.45% Senior Notes due 2019 399,873 399,805 $400 million 5.00% Senior Notes due 2021 399,245 399,025 $400 million 4.70% Senior Notes due 2023 399,138 398,986 $400 million 3.95% Senior Notes due 2026 399,987 399,985 $100 million 4.09% Promissory Note due 2039 91,787 94,370 $400 million 6.20% Subordinated Debentures due 2042 400,000 400,000 $400 million 5.75% Subordinated Debentures due 2056 400,000 400,000 $400 million Variable Rate Junior Subordinated Debentures due 2065 318,740 318,737 Sub-total 2,808,770 3,110,853 Unamortized issuance costs (20,405 ) (22,218 ) Long-term Debt $ 2,788,365 $ 3,088,635 In June 2016, RGA issued 3.95% Senior Notes due September 15, 2026 with a face amount of $400.0 million and 5.75% Fixed-To-Floating Rate Subordinated Debentures due June 15, 2056 with a face amount of $400.0 million . These securities have been registered with the Securities and Exchange Commission. The net proceeds from these offerings were approximately $791.2 million and were used in part to repay upon maturity the Company’s $300.0 million 5.625% Senior Notes that matured in March 2017. The remainder was used for general corporate purposes. Capitalized issue costs were approximately $8.8 million . In December 2015, the interest rate on RGA’s Junior Subordinated Debentures with a face amount of $400.0 million converted from a fixed rate of 6.75% to a floating rate equal to the three-month LIBOR plus 266.5 basis points. The Company entered into an interest rate swap that commenced in December 2017, effectively fixing the interest rate on these securities at 4.82% until December 2037. Certain of the Company’s debt agreements contain financial covenant restrictions related to, among others, liens, the issuance and disposition of stock of restricted subsidiaries, minimum requirements of consolidated net worth, maximum ratios of debt to capitalization and change of control provisions. A material ongoing covenant default could require immediate payment of the amount due, including principal, under the various agreements. Additionally, the Company’s debt agreements contain cross-default covenants, which would make outstanding borrowings immediately payable in the event of a material uncured covenant default under any of the agreements, including, but not limited to, non-payment of indebtedness when due for an amount in excess of the amounts set forth in those agreements, bankruptcy proceedings, or any other event which results in the acceleration of the maturity of indebtedness. As of December 31, 2017 and 2016 , the Company had $2,808.8 million and $3,110.9 million , respectively, in outstanding borrowings under its debt agreements and was in compliance with all covenants under those agreements. As of December 31, 2017 and 2016 , the average interest rate on long-term debt outstanding was 5.24% and 5.16% , respectively. The ability of the Company to make debt principal and interest payments depends on the earnings and surplus of subsidiaries, investment earnings on undeployed capital proceeds, and the Company’s ability to raise additional funds. Future principal payments due on long-term debt, excluding discounts, as of December 31, 2017 , were as follows (dollars in thousands): Calendar Year 2018 2019 2020 2021 2022 Thereafter Long-term debt $ 2,690 $ 402,802 $ 2,919 $ 403,040 $ 3,167 $ 1,996,972 Credit and Committed Facilities The Company has obtained bank letters of credit in favor of various affiliated and unaffiliated insurance companies from which the Company assumes business. These letters of credit represent guarantees of performance under the reinsurance agreements and allow ceding companies to take statutory reserve credits. Certain of these letters of credit contain financial covenant restrictions. At December 31, 2017 and 2016 , there were approximately $120.1 million and $189.4 million , respectively, of undrawn outstanding bank letters of credit in favor of third parties. Additionally, the Company utilizes letters of credit primarily to secure reserve credits when it retrocedes business to its affiliated subsidiaries. The Company cedes business to its affiliates to help reduce the amount of regulatory capital required in certain jurisdictions such as the U.S. and the United Kingdom. As of December 31, 2017 and 2016 , $1,492.2 million and $1,010.8 million , respectively, in undrawn letters of credit from various banks were outstanding, primarily backing reinsurance between the various subsidiaries of the Company. The banks providing letters of credit to the Company are included on the NAIC list of approved banks. The Company maintains nine committed credit facilities, a syndicated revolving credit facility with a capacity of $850.0 million and eight letter of credit facilities with a combined capacity of $1,266.5 million . The Company may borrow cash and obtain letters of credit in multiple currencies under its syndicated revolving credit facility. The following table provides additional information on the Company’s existing committed credit facilities as of December 31, 2017 and 2016 (dollars in thousands): Amount Utilized (1) December 31, Current Capacity Maturity Date 2017 2016 Basis of Fees $180,403 (2) November 2018 $ 8,638 $ 31,382 Fixed 5,952 (2) March 2019 5,952 17,513 Fixed 850,000 September 2019 96,564 96,095 Senior unsecured long-term debt rating 188,000 October 2019 188,000 270,000 Fixed 117,135 (2) December 2019 117,135 72,080 Fixed 100,000 June 2020 75,573 70,690 Fixed 100,000 May 2021 100,000 — Fixed 75,000 June 2021 61,900 85,040 Fixed 500,000 May 2022 500,000 — Fixed (1) Represents issued but undrawn letters of credit. There was no cash borrowed for the periods presented. (2) Foreign currency denominated facility, amounts presented are in U.S. dollars. Fees associated with the Company’s other letters of credit are not fixed for periods in excess of one year and are based on the Company’s ratings and the general availability of these instruments in the marketplace. Total fees expensed associated with the Company’s letters of credit were $10.5 million , $7.9 million and $10.9 million for the years ended December 31, 2017, 2016 and 2015 , respectively, and are included in policy acquisition costs and other insurance expenses.

Collateral Finance and Securiti

Collateral Finance and Securitization Notes	12 Months Ended
	Dec. 31, 2017
Collateralized Financings [Abstract]
Collateral Finance and Securitization Notes	COLLATERAL FINANCE AND SECURITIZATION NOTES Collateral Finance Notes In June 2006 , RGA’s subsidiary, Timberlake Financial L.L.C. (“Timberlake Financial”), issued $850.0 million of Series A Floating Rate Insured Notes, due June 2036, in a private placement. The notes were issued to fund the collateral requirements for statutory reserves required by Regulation XXX on specified term life insurance policies reinsured by RGA Reinsurance and retroceded to Timberlake Re. Proceeds from the notes, along with a $112.8 million direct investment by RGA, were deposited into a series of accounts that collateralize the notes and are not available to satisfy the general obligations of the Company. As of December 31, 2017 and 2016 , respectively, the Company held assets in trust and in custody of $841.5 million and $893.8 million , of which $39.7 million and $24.1 million were held in a Debt Service Coverage account to cover interest payments on the notes. Interest on the notes accrues at an annual rate of 1-month LIBOR plus a base rate margin, payable monthly, and totaled $6.4 million , $4.2 million and $3.8 million in 2017, 2016 and 2015 , respectively. In May 2015, RGA’s subsidiary, RGA Reinsurance Company (Barbados) Ltd. (“RGA Barbados”) obtained CAD$200.0 million of collateral financing from a third party through 2020, enabling RGA Barbados to support collateral requirements for Canadian reinsurance transactions. Capitalized issuance costs were approximately $1.3 million . The obligation is reflected on the consolidated balance sheets in collateral finance and securitization notes. Interest on the collateral financing is payable quarterly and accrues at 3-month Canadian Dealer Offered Rate plus a margin and totaled $4.2 million , $4.0 million and $2.3 million in 2017, 2016 and 2015 , respectively. In October 2015, RGA’s subsidiary, RGA Americas Reinsurance Company, Ltd. (“RGA Americas”), entered into a collateral financing transaction pursuant to which it issued a CAD$150 million note and, in return, obtained a CAD$150 million demand note issued by a designated series of a Delaware master trusts. The demand note matures in October 2020 and is used to support collateral requirements for Canadian reinsurance transactions. The demand note is secured by a portfolio of specified assets that have an aggregate market value at least equal to the principal amount of the demand note and a payment obligation pledged by a third party financial institution. The principal amount of the demand note is payable upon demand by the holder, which creates a corresponding payment under the note issued by RGA Americas. The note issued by RGA Americas bears interest at a rate equal to the rate on the corresponding demand note, plus an amount representing fees payable to the applicable third party financial institution. Through December 31, 2017, no principal payments have been received or are currently due on the demand note and, as a result, there was no payment obligation under the note issued by RGA Americas. Accordingly, the notes are not reflected in the Company’s consolidated balance sheet or the table below, as of that date. Capitalized issuance costs were approximately $2.4 million . Securitization Notes In December 2014, RGA’s subsidiary, Chesterfield Financial Holdings LLC, (“Chesterfield Financial”), issued $300.0 million of asset-backed notes due December 2024 in a private placement. The notes were issued as part of an embedded value securitization transaction covering a closed block of policies assumed by RGA Reinsurance and retroceded to Chesterfield Re. Proceeds from the notes, along with a direct investment by the Company, were applied by Chesterfield Financial to (i) pay certain transaction-related expenses, (ii) establish a reserve account owned by Chesterfield Financial and pledged to the indenture trustee for the benefit of the holders of the notes (primarily to cover interest payments on the notes), and (iii) to fund an initial stock purchase from and capital contribution to Chesterfield Re to capitalize Chesterfield Re and to finance the payment of a ceding commission by Chesterfield Re to RGA Reinsurance under the retrocession agreement. Capitalized issuance costs were approximately $5.4 million . As of December 31, 2017 and 2016 , the Company held deposits in trust of $19.4 million and $22.1 million , respectively, to cover interest payments on the notes, which are not available to satisfy the general obligations of the Company. Interest on the notes accrues at an annual rate of 4.50% , payable quarterly, and totaled $11.3 million , $13.1 million and $14.0 million in 2017, 2016 and 2015 , respectively. The notes represent senior, secured indebtedness of Chesterfield Financial. Limited support is provided by RGA for temporary potential liquidity events at Chesterfield Financial and for temporary potential statutory capital and surplus events at Chesterfield Re. Otherwise, there is no legal recourse to RGA or its other subsidiaries. The notes are not insured or guaranteed by any other person or entity. The Company’s collateral finance and securitization notes consist of the following as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Timberlake Financial $ 411,951 $ 451,880 RGA Barbados 159,100 148,820 Chesterfield Financial 217,800 246,300 Unamortized issuance costs (4,913 ) (6,300 ) Total $ 783,938 $ 840,700

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION The Company has geographic-based and business-based operational segments. Geographic-based operations are further segmented into traditional and financial solutions businesses. The U.S. and Latin America Traditional segment provides individual and group life and health reinsurance to domestic clients for a variety of products through yearly renewable term agreements, coinsurance, and modified coinsurance. The U.S. and Latin America Financial Solutions segment includes asset-intensive products that concentrate on the investment risk within underlying annuities and corporate-owned life insurance policies, and financial reinsurance that assists ceding companies in meeting applicable regulatory requirements while enhancing their financial strength and regulatory surplus position. The Canada Traditional segment is primarily engaged in individual life reinsurance, as well as creditor, group life and health, critical illness and disability reinsurance, through yearly renewable term and coinsurance agreements. The Canada Financial Solutions segment concentrates on assisting clients with longevity risk transfer structures within underlying annuities and pension benefit obligations, and on assisting clients in meeting applicable regulatory requirements while enhancing their financial strength and regulatory surplus position through financial reinsurance structures. The Europe, Middle East and Africa Traditional segment provides individual and group life and health products through yearly renewable term and coinsurance agreements, reinsurance of critical illness coverage that provides a benefit in the event of the diagnosis of a pre-defined critical illness and underwritten annuities. The Europe, Middle East and Africa Financial Solutions segment provides longevity, asset-intensive and financial reinsurance. Longevity reinsurance takes the form of closed block annuity reinsurance and longevity swap structures. The Asia Pacific Traditional segment provides individual and group life and health reinsurance, critical illness coverage, disability and superannuation through yearly renewable term and coinsurance agreements. The Asia Pacific Financial Solutions segment provides financial reinsurance, asset-intensive and certain disability and life blocks. Corporate and Other operations include investment income from invested assets not allocated to support segment operations and proceeds from the Company’s capital-raising efforts that have not been deployed yet, in addition to investment related gains or losses. Additionally, Corporate and Other includes results associated with the Company’s collateral finance and securitization notes and results from certain wholly-owned subsidiaries and joint ventures that, among other activities, develop and market technology solutions for the insurance industry. The accounting policies of the segments are the same as those described in Note 2 – “Summary of Significant Accounting Policies.” The Company measures segment performance primarily based on profit or loss from operations before income taxes. There are no intersegment reinsurance transactions and the Company does not have any material long-lived assets. The Company allocates capital to its segments based on an internally developed economic capital model, the purpose of which is to measure the risk in the business and to provide a basis upon which capital is deployed. The economic capital model considers the unique and specific nature of the risks inherent in the Company’s businesses. As a result of the economic capital allocation process, a portion of investment income is attributed to the segments based on the level of allocated capital. In addition, the segments are charged for excess capital utilized above the allocated economic capital basis. This charge is included in policy acquisition costs and other insurance expenses. Information related to revenues, income (loss) before income taxes, interest expense, depreciation and amortization, and assets of the Company’s operations are summarized below (dollars in thousands): For the years ended December 31, 2017 2016 2015 Revenues: U.S. and Latin America: Traditional $ 6,100,171 $ 5,964,968 $ 5,465,026 Financial Solutions 1,150,378 840,446 643,865 Total 7,250,549 6,805,414 6,108,891 Canada: Traditional 1,103,520 1,118,004 1,023,012 Financial Solutions 48,938 46,938 45,034 Total 1,152,458 1,164,942 1,068,046 Europe, Middle East and Africa: Traditional 1,362,075 1,195,149 1,190,742 Financial Solutions 311,071 340,518 286,666 Total 1,673,146 1,535,667 1,477,408 Asia Pacific: Traditional 2,210,686 1,771,150 1,638,357 Financial Solutions 73,775 63,382 56,581 Total 2,284,461 1,834,532 1,694,938 Corporate and Other 155,155 180,956 68,895 Total $ 12,515,769 $ 11,521,511 $ 10,418,178 For the years ended December 31, 2017 2016 2015 Income (loss) before income taxes: U.S. and Latin America: Traditional $ 373,434 $ 371,101 $ 235,771 Financial Solutions 401,584 283,380 207,963 Total 775,018 654,481 443,734 Canada: Traditional 120,218 134,705 124,175 Financial Solutions 16,643 7,945 13,902 Total 136,861 142,650 138,077 Europe, Middle East and Africa: Traditional 70,486 30,059 48,410 Financial Solutions 123,514 138,007 108,445 Total 194,000 168,066 156,855 Asia Pacific: Traditional 148,786 113,928 105,654 Financial Solutions 13,130 4,063 19,619 Total 161,916 117,991 125,273 Corporate and Other (124,980 ) (39,242 ) (119,144 ) Total $ 1,142,815 $ 1,043,946 $ 744,795 For the years ended December 31, 2017 2016 2015 Interest expense: Corporate and Other $ 146,025 $ 137,623 $ 142,863 Total $ 146,025 $ 137,623 $ 142,863 For the years ended December 31, 2017 2016 2015 Depreciation and amortization: U.S. and Latin America: Traditional $ 284,959 $ 271,732 $ 218,974 Financial Solutions 208,790 155,560 44,275 Total 493,749 427,292 263,249 Canada: Traditional 24,057 22,170 23,887 Financial Solutions 10 11 — Total 24,067 22,181 23,887 Europe, Middle East and Africa: Traditional 35,000 46,562 60,193 Financial Solutions 91 72 — Total 35,091 46,634 60,193 Asia Pacific: Traditional 114,333 45,562 31,955 Financial Solutions 1,448 1,492 217 Total 115,781 47,054 32,172 Corporate and Other 37,276 13,894 16,495 Total $ 705,964 $ 557,055 $ 395,996 The table above includes amortization of DAC, including the effect from investment related gains and losses. For the years ended December 31, 2017 2016 Assets: U.S. and Latin America: Traditional $ 18,603,423 $ 18,140,825 Financial Solutions 15,959,206 13,712,106 Total 34,562,629 31,852,931 Canada: Traditional 4,161,452 3,846,682 Financial Solutions 126,372 85,405 Total 4,287,824 3,932,087 Europe, Middle East and Africa: Traditional 3,099,495 2,559,124 Financial Solutions 5,274,993 3,876,131 Total 8,374,488 6,435,255 Asia Pacific: Traditional 4,915,442 3,968,081 Financial Solutions 1,198,585 676,281 Total 6,114,027 4,644,362 Corporate and Other 7,175,850 6,233,244 Total $ 60,514,818 $ 53,097,879 Companies in which RGA has significant influence over the operating and financing decisions but are not required to be consolidated, are reported on the equity basis of accounting. The equity in the net income of such investments is not material to the results of operations or financial position of individual segments or the Company taken as a whole. Capital expenditures of each reporting segment were immaterial in the periods noted. No individual client generated 10% or more of the Company’s total gross premiums on a consolidated basis in 2017, 2016 and 2015 . For the purpose of this disclosure, companies that are within the same insurance holding company structure are combined.

Short-Duration Contracts

Short-Duration Contracts	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Short-Duration Insurance and Deposit Contracts [Text Block]	SHORT-DURATION CONTRACTS The Company uses several actuarial methods to compute incurred-but-not reported liabilities. These methods use historical claim reporting patterns to develop a triangle of reported claim amounts. The claim triangle is then used to develop the ultimate claims amount and the incurred-but-not reported liabilities. Expected claim methods use exposure data such as premiums to develop the ultimate claim amount. The final method blends the estimates from the development and the expected claim methods. The Company did not make significant changes to the methods used to compute the incurred-but-not reported liabilities in 2017. The following tables provide information on incurred and paid claims development, net of retrocession, for short-duration reinsurance contracts for the Company’s U.S. and Latin America and Asia Pacific Traditional segments, which primarily relate to group life and health (including disability) business. The short-duration business for the Company’s other segments is immaterial. Liabilities for claims and claims adjustment expenses, net of reinsurance equals total incurred claims less cumulative paid claims plus outstanding liabilities prior to 2012. The Company provides reinsurance on large quota share transactions. It is common industry practice for cedants to provide loss information on a bulk basis without comprehensive claim details. Additionally, a claim under aggregate stop loss coverage may be the result of thousands of claims, but the Company only pays the excess amount. Therefore, it is impractical to provide meaningful claim count detail by accident year in the tables shown below. U.S. and Latin America As of (in thousands) December 31, 2017 Incurred Claims and Allocated Claim Adjustments, Net of Reinsurance (1) Total of Incurred-but-Not-Reported Liabilities Plus Expected Development on Reported Claims For the Years Ended December 31, Accident Year 2012 2013 2014 2015 2016 2017 2012 $ 322,579 $ 309,119 $ 297,037 $ 298,262 $ 299,098 $ 297,688 $ 24 2013 349,262 332,907 338,977 336,552 336,436 164 2014 407,953 411,373 396,383 397,151 1,597 2015 459,524 460,917 465,167 3,809 2016 500,843 499,785 23,149 2017 485,442 200,109 Total $ 2,481,669 Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net of Reinsurance (1) For the Years Ended December 31, Accident Year 2012 2013 2014 2015 2016 2017 2012 $ 109,323 $ 222,139 $ 243,890 $ 252,018 $ 258,297 $ 263,565 2013 114,457 248,828 277,130 285,817 292,067 2014 128,813 304,578 337,081 349,078 2015 146,196 360,658 407,282 2016 184,940 392,517 2017 189,853 Total $ 1,894,362 All outstanding claims prior to 2012, net of reinsurance 208,874 Liabilities for claims and claim adjustment expense, net of reinsurance $ 796,181 (1) 2012-2016 Unaudited. Asia Pacific As of (in thousands) December 31, 2017 Incurred Claims and Allocated Claim Adjustments, Net of Reinsurance (1) Total of Incurred-but-Not-Reported Liabilities Plus Expected Development on Reported Claims For the Years Ended December 31, Accident Year 2012 2013 2014 2015 2016 2017 2012 $ 230,295 $ 309,090 $ 313,862 $ 317,536 $ 325,992 $ 336,901 $ 13,196 2013 324,334 346,886 336,531 333,639 347,865 21,310 2014 306,919 332,718 294,049 300,025 27,113 2015 308,517 284,871 277,166 44,713 2016 252,197 228,342 62,959 2017 235,146 140,159 Total $ 1,725,445 Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net of Reinsurance (1) For the Years Ended December 31, Accident Year 2012 2013 2014 2015 2016 2017 2012 $ 54,638 $ 149,912 $ 205,303 $ 247,028 $ 269,808 $ 287,941 2013 55,175 159,799 231,919 261,359 289,472 2014 38,241 150,295 196,570 228,405 2015 54,241 131,364 185,393 2016 42,440 108,310 2017 39,262 Total $ 1,138,783 All outstanding claims prior to 2012, net of reinsurance 144,984 Liabilities for claims and claim adjustment expense, net of reinsurance $ 731,646 (1) 2012-2016 Unaudited. The reconciliation of the net incurred and paid claims development tables to the liability for claims and claim adjustment expense in the consolidated balance sheets as of December 31, 2017 and 2016 , are as follows: 2017 Liabilities for claims and claim adjustment expense, net of reinsurance: U.S. and Latin America $ 796,181 Asia Pacific 731,646 Liabilities for claims and claim adjustment expense, net of reinsurance 1,527,827 Adjustments to reconcile to total policy claims and future policy benefits: Reinsurance recoverable 17,940 Effect of discounting and unallocated claims adjustment expense (146,331 ) Total adjustments (128,391 ) Other short-duration contracts: Canada 150,248 Europe, Middle East and Africa 346,916 Other 122,690 Total short-duration contracts 2,019,290 Other than short-duration contracts 25,336,025 Total future policy benefits and other policy claims and benefits $ 27,355,315 The following is unaudited supplementary information about average historical claims duration as of December 31, 2017 : Average Annual Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 U.S. and Latin America 35.1 % 41.9 % 8.5 % 2.8 % 2.0 % 1.8 % Asia Pacific 16.5 % 30.3 % 18.0 % 10.5 % 7.6 % 5.4 %

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE The following table sets forth the computation of basic and diluted earnings per share on net income (in thousands, except per share information): 2017 2016 2015 Earnings: Net income (numerator for basic and diluted calculations) $ 1,822,181 $ 701,443 $ 502,166 Shares: Weighted average outstanding shares (denominator for basic calculations) 64,427 64,274 66,553 Equivalent shares from outstanding stock options 1,326 715 739 Diluted shares (denominator for diluted calculations) 65,753 64,989 67,292 Earnings per share: Basic $ 28.28 $ 10.91 $ 7.55 Diluted 27.71 10.79 7.46 The calculation of common equivalent shares does not include the impact of options having a strike or conversion price that exceeds the average stock price for the earnings period, as the result would be antidilutive. The calculation of common equivalent shares also excludes the impact of outstanding performance contingent shares, as the conditions necessary for their issuance have not been satisfied as of the end of the reporting period. Approximately 0.2 million and 0.3 million outstanding stock options were not included in the calculation of common equivalent shares during 2017 and 2015, respectively. During 2016, all outstanding options were included in the calculation of common equivalent shares. Approximately 0.3 million , 0.4 million and 0.4 million performance contingent shares were excluded from the calculation of common equivalent shares during 2017 , 2016 and 2015 , respectively.

Equity

Equity	12 Months Ended
	Dec. 31, 2017
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Comprehensive Income	EQUITY Common stock The changes in number of common stock shares, issued, held in treasury and outstanding are as follows for the periods indicated: Issued Held In Treasury Outstanding Balance, December 31, 2014 79,137,758 10,364,797 68,772,961 Common Stock acquired — 4,145,440 (4,145,440 ) Stock-based compensation (1) — (577,005 ) 577,005 Balance, December 31, 2015 79,137,758 13,933,232 65,204,526 Common Stock acquired — 1,356,892 (1,356,892 ) Stock-based compensation (1) — (454,868 ) 454,868 Balance, December 31, 2016 79,137,758 14,835,256 64,302,502 Common Stock acquired — 208,680 (208,680 ) Stock-based compensation (1) — (358,273 ) 358,273 Balance, December 31, 2017 79,137,758 14,685,663 64,452,095 (1) Represents net shares issued from treasury pursuant to the Company’s stock-based compensation programs. Common stock held in treasury Common stock held in treasury is accounted for at average cost. Gains resulting from the reissuance of “Common stock held in treasury” are credited to “Additional paid-in capital.” Losses resulting from the reissuance of “Common stock held in treasury” are charged first to “Additional paid-in capital” to the extent the Company has previously recorded gains on treasury share transactions, then to “Retained earnings.” During 2015, RGA’s board of directors authorized and amended a share repurchase program, with no expiration date, to repurchase up to $450.0 million of RGA’s outstanding common stock. In connection with this authorization, the board of directors terminated the stock repurchase authority granted in 2014. During 2015, RGA repurchased 4,145,440 shares of common stock under this program for $375.3 million . During 2016, RGA’s board of directors authorized and amended a share repurchase program, with no expiration date, to repurchase up to $400.0 million of RGA’s outstanding common stock. In connection with this authorization, the board of directors terminated the stock repurchase authority granted in 2015. During 2016, RGA repurchased 1,356,892 shares of common stock under this program for $116.5 million . During 2017, RGA’s board of directors authorized and amended a share repurchase program, with no expiration date, to repurchase up to $400.0 million of RGA’s outstanding common stock. In connection with this authorization, the board of directors terminated the stock repurchase authority granted in 2016. During 2017, RGA repurchased 208,680 shares of common stock under this program for $26.9 million . Accumulated other comprehensive income (loss) The following table presents the components of the Company’s other comprehensive income (loss) for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): For the year ended December 31, 2017 : Before-Tax Amount Tax (Expense) Benefit After-Tax Amount Foreign currency translation adjustments: Change arising during year $ 74,926 $ 25,369 $ 100,295 Foreign currency swap (47,953 ) 16,784 (31,169 ) Net foreign currency translation adjustments 26,973 42,153 69,126 Unrealized gains on investments: (1) Unrealized net holding gains arising during the year 1,029,591 (313,729 ) 715,862 Less: Reclassification adjustment for net gains realized in net income 25,039 (7,011 ) 18,028 Net unrealized gains 1,004,552 (306,718 ) 697,834 Change in unrealized OTTI on fixed maturity securities 375 (131 ) 244 Unrealized pension and postretirement benefits: Net prior service cost arising during the year 11,717 (4,095 ) 7,622 Net gain arising during the period (10,587 ) 3,691 (6,896 ) Unrealized pension and postretirement benefits, net 1,130 (404 ) 726 Other comprehensive income (loss) $ 1,033,030 $ (265,100 ) $ 767,930 For the year ended December 31, 2016 : Before-Tax Amount Tax (Expense) Benefit After-Tax Amount Foreign currency translation adjustments: Change arising during year $ 39,925 $ (24,663 ) $ 15,262 Foreign currency swap (10,234 ) 3,582 (6,652 ) Net foreign currency translation adjustments 29,691 (21,081 ) 8,610 Unrealized gains on investments: (1) Unrealized net holding gains arising during the year 641,606 (180,448 ) 461,158 Less: Reclassification adjustment for net gains realized in net income 65,798 (23,029 ) 42,769 Net unrealized gains 575,808 (157,419 ) 418,389 Change in unrealized OTTI on fixed maturity securities 1,457 (510 ) 947 Unrealized pension and postretirement benefits: Net prior service cost arising during the year 444 (149 ) 295 Net gain arising during the period 4,427 (1,623 ) 2,804 Unrealized pension and postretirement benefits, net 4,871 (1,772 ) 3,099 Other comprehensive income (loss) $ 611,827 $ (180,782 ) $ 431,045 For the year ended December 31, 2015: Before-Tax Amount Tax (Expense) Benefit After-Tax Amount Foreign currency translation adjustments: Change arising during year $ (342,539 ) $ 17,129 $ (325,410 ) Foreign currency swap 96,019 (33,607 ) 62,412 Net foreign currency translation adjustments (246,520 ) (16,478 ) (262,998 ) Unrealized losses on investments: (1) Unrealized net holding losses arising during the year (1,084,732 ) 359,407 (725,325 ) Less: Reclassification adjustment for net losses realized in net income (55,767 ) 19,518 (36,249 ) Net unrealized losses (1,028,965 ) 339,889 (689,076 ) Unrealized pension and postretirement benefits: Net prior service cost arising during the year 337 (107 ) 230 Net loss arising during the period 4,618 (1,619 ) 2,999 Unrealized pension and postretirement benefits, net 4,955 (1,726 ) 3,229 Other comprehensive income (loss) $ (1,270,530 ) $ 321,685 $ (948,845 ) (1) Includes cash flow hedges. See Note 5 for additional information on cash flow hedges. A summary of the components of net unrealized appreciation (depreciation) of balances carried at fair value is as follows (dollars in thousands): For the years ended December 31, 2017 2016 2015 Change in net unrealized appreciation (depreciation) on: Fixed maturity securities available-for-sale $ 987,570 $ 561,906 $ (1,055,458 ) Other investments (1) 25,577 18,900 8,983 Effect on unrealized appreciation on: Deferred policy acquisition costs (8,220 ) (3,541 ) 17,510 Net unrealized appreciation (depreciation) $ 1,004,927 $ 577,265 $ (1,028,965 ) (1) Includes cash flow hedges. See Note 5 for additional information on cash flow hedges. The balance of and changes in each component of AOCI were as follows (dollars in thousands): Accumulated Currency Translation Adjustments Unrealized Appreciation (Depreciation) of Investments (1) Pension and Postretirement Benefits Accumulated Other Comprehensive Income (Loss) Balance, December 31, 2014 $ 81,847 $ 1,624,773 $ (49,491 ) $ 1,657,129 OCI before reclassifications (246,520 ) (1,101,760 ) (1,248 ) (1,349,528 ) Amounts reclassified from AOCI — 72,795 6,203 78,998 Deferred income tax benefit (expense) (16,478 ) 339,889 (1,726 ) 321,685 Balance, December 31, 2015 (181,151 ) 935,697 (46,262 ) 708,284 OCI before reclassifications 29,691 646,887 (951 ) 675,627 Amounts reclassified from AOCI — (69,622 ) 5,822 (63,800 ) Deferred income tax benefit (expense) (21,081 ) (157,929 ) (1,772 ) (180,782 ) Balance, December 31, 2016 (172,541 ) 1,355,033 (43,163 ) 1,139,329 OCI before reclassifications 26,973 1,039,387 (4,273 ) 1,062,087 Amounts reclassified from AOCI — (34,460 ) 5,403 (29,057 ) Deferred income tax benefit (expense) 42,153 (306,849 ) (404 ) (265,100 ) Adoption of new accounting standard 17,065 147,550 (8,243 ) 156,372 Balance, December 31, 2017 $ (86,350 ) $ 2,200,661 $ (50,680 ) $ 2,063,631 (1) Includes cash flow hedges of $2,619 , $(2,496) and $(29,397) as of December 31, 2017, 2016 and 2015 , respectively. See Note 5 for additional information on cash flow hedges. The following table presents the amounts of AOCI reclassifications for the years ended December 31, 2017 and 2016 (dollars in thousands): Amount Reclassified from AOCI Details about AOCI Components 2017 2016 Affected Line Item in Statement of Income Net unrealized investment gains (losses): Net unrealized gains and losses on available-for-sale securities $ 25,039 $ 65,798 Investment related gains (losses), net OTTI on fixed maturity securities — 74 Investment related gains (losses), net Cash flow hedges - Interest rate (79 ) — (1) Cash flow hedges - Currency/Interest rate 380 510 (1) Cash flow hedges - Forward bond purchase commitments 900 (301 ) (1) Deferred policy acquisition costs attributed to unrealized gains and losses 8,220 3,541 (2) Total 34,460 69,622 Provision for income taxes (10,308 ) (17,672 ) Net unrealized gains (losses), net of tax $ 24,152 $ 51,950 Amortization of defined benefit plan items: Prior service cost (credit) $ 971 $ 328 (3) Actuarial gains/(losses) (6,374 ) (6,150 ) (3) Total (5,403 ) (5,822 ) Provision for income taxes 1,891 2,038 Amortization of defined benefit plans, net of tax $ (3,512 ) $ (3,784 ) Total reclassifications for the period $ 20,640 $ 48,166 (1) See Note 5 for information on cash flow hedges. (2) See Note 8 for information on deferred policy acquisition costs. (3) See Note 10 for information on employee benefit plans.

Equity Based Compensation

Equity Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity Based Compensation	Equity Based Compensation The Company adopted the RGA Flexible Stock Plan (the “Plan”) in February 1993, as amended, and the Flexible Stock Plan for Directors (the “Directors Plan”) in January 1997, as amended, (collectively, the “Stock Plans”). The Stock Plans provide for the award of benefits (collectively “Benefits”) of various types, including stock options, stock appreciation rights (“SARs”), restricted stock, performance shares, cash awards, and other stock-based awards, to key employees, officers, directors and others performing significant services for the benefit of the Company or its subsidiaries. As of December 31, 2017 , shares authorized for the granting of Benefits under the Plan and the Directors Plan totaled 14,960,077 and 412,500 respectively. The Company uses treasury shares or shares made available from authorized but unissued shares to support the future exercise of options or settlement of awards granted under its stock plans. Equity-based compensation expense of $22.3 million , $33.1 million , and $16.0 million related to grants or awards under the Stock Plans was recognized in 2017, 2016 and 2015 , respectively. Equity-based compensation expense is principally related to the issuance of stock options, performance contingent restricted units, stock appreciation rights and restricted stock. In general, options granted under the Plan become exercisable over vesting periods ranging from one to five years. Options are generally granted with an exercise price equal to the stock’s fair value at the date of grant and expire 10 years after the date of grant. There are no options outstanding under the Directors Plan during the periods presented. Information with respect to grants under the Stock Plans follows. Stock Options The following table presents a summary of stock option activity: Number of Options Weighted-Average Exercise Price Aggregate Intrinsic Value (in millions) Outstanding December 31, 2016 2,573,223 $ 68.70 Granted 171,388 $ 129.72 Exercised (430,429 ) $ 58.07 Forfeited (4,413 ) $ 87.15 Outstanding December 31, 2017 2,309,769 $ 75.17 $ 186.5 Options exercisable 1,700,629 $ 66.04 $ 152.9 The intrinsic value of options exercised was $42.1 million , $41.4 million , and $26.2 million for 2017, 2016 and 2015 , respectively. Options Outstanding Options Exercisable Range of Exercise Prices Number Outstanding as of 12/31/2017 Weighted-Average Remaining Contractual Life (years) Weighted- Average Exercise Price Number Exercisable as of 12/31/2017 Weighted-Average Exercise Price $0.00 - $49.99 245,264 1.7 $ 40.54 245,264 $ 40.54 $50.00 - $59.99 902,246 4.4 $ 58.23 902,246 $ 58.23 $60.00 - $69.99 839 5.2 $ 60.24 839 $ 60.24 $70.00 - $79.99 190,137 6.2 $ 78.48 190,137 $ 78.48 $90.00 + 971,283 8.1 $ 99.02 362,143 $ 96.22 Totals 2,309,769 5.8 $ 75.17 1,700,629 $ 66.04 The following table presents the weighted average assumptions used to determine the fair value of stock options issued: For the years ended December 31, 2017 2016 2015 Dividend yield 1.26 % 1.58 % 1.47 % Risk-free rate of return 2.32 % 1.69 % 2.04 % Expected volatility 22.8 % 28.1 % 35.0 % Expected life (years) 7.0 7.0 7.0 Weighted average exercise price of stock options granted $ 129.72 $ 93.53 $ 91.65 Weighted average fair value of stock options granted $ 31.57 $ 24.52 $ 30.50 The Black-Scholes model was used to determine the fair value recognized in the financial statements of stock options that have been granted. The Company used daily historical volatility when calculating stock option values. The benchmark rate is based on observed interest rates for instruments with maturities similar to the expected term of the stock options. Dividend yield is determined based on historical dividend distributions compared to the price of the underlying common stock as of the valuation date and held constant over the life of the stock options. The Company estimated expected life using the historical average years to exercise or cancellation. Performance Shares Performance shares, also referred to as performance contingent units (“PCUs”), are units that, if they vest, are multiplied by a performance factor to produce a number of final PCUs which are paid in the Company’s common stock. Each PCU represents the right to receive up to two shares of Company common stock, depending on the results of certain performance measures over a three -year period. The compensation expense related to the PCUs is recognized ratably over the requisite performance period. Performance shares are accounted for as equity awards, but are not credited with dividend-equivalents for actual dividends paid on the Company’s common stock during the performance period. Restricted Stock Units In general, restricted stock units (“RSUs”) become payable at the end of a three- or ten-year vesting period. Each RSU, if they vest, represents the right to receive one share of Company common stock. RSUs awarded under the plan generally have no strike price and are included in the Company’s shares outstanding. The following table presents a summary of Performance Share and Restricted Stock Unit activity: Performance Contingent Units Restricted Stock Units Outstanding December 31, 2016 585,971 96,628 Granted 115,176 22,971 Paid (137,083 ) (38,843 ) Forfeited (100,805 ) (3,398 ) Outstanding December 31, 2017 463,259 77,358 During 2017, the Company issued 115,176 PCUs to key employees at a weighted average fair value per unit of $129.72 . In May 2017 and May 2016, RGA’s board of directors approved a 0.75 and 0.40 share payout for each PCU granted in 2014 and 2013, resulting in the issuance of 137,083 and 94,436 shares of common stock from treasury, respectively. As of December 31, 2017 , the total compensation cost of non-vested awards not yet recognized in the financial statements was $26.3 million . It is estimated that these costs will vest over a weighted average period of 1.5 years. The majority of the awards granted each year under the board-approved incentive compensation package and Directors Plan are made in the first quarter of each year.

Quarterly Results of Operations

Quarterly Results of Operations	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) Years Ended December 31, (in thousands, except per share data) 2017 First Second Third Fourth Total Revenues $ 3,008,740 $ 3,129,276 $ 3,145,310 $ 3,232,443 Total benefits and expenses 2,800,896 2,789,961 2,805,148 2,976,949 Income before income taxes 207,844 339,315 340,162 255,494 Net Income 145,512 232,190 227,591 1,216,888 Earnings Per Share: Basic earnings per share $ 2.26 $ 3.60 $ 3.53 $ 18.89 Diluted earnings per share 2.22 3.54 3.47 18.49 2016 First Second Third Fourth Total Revenues $ 2,512,568 $ 3,039,068 $ 2,900,577 $ 3,069,298 Total benefits and expenses 2,404,988 2,685,845 2,612,977 2,773,755 Income before income taxes 107,580 353,223 287,600 295,543 Net Income 76,472 236,103 198,719 190,149 Earnings Per Share: Basic earnings per share $ 1.18 $ 3.68 $ 3.10 $ 2.96 Diluted earnings per share 1.17 3.64 3.07 2.92

Summary of Investments Other Th

Summary of Investments Other Than Investments in Related Parties	12 Months Ended
	Dec. 31, 2017
Summary of Investments, Other than Investments in Related Parties [Abstract]
Summary of Investments Other Than Investments in Related Parties	REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE I-SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES December 31, 2017 (in millions) Type of Investment Cost Fair Value Amount at Which Shown in the Balance Sheets (1) Fixed maturity securities: Bonds: United States government and government agencies and authorities $ 1,953 $ 1,944 $ 1,944 State and political subdivisions 648 703 703 Foreign governments (2) 6,098 7,621 7,621 Public utilities 2,454 2,649 2,649 Mortgage-backed and asset-backed securities 4,615 4,672 4,672 All other corporate bonds 19,513 20,562 20,562 Total fixed maturity securities 35,281 38,151 38,151 Equity securities: Non-redeemable preferred stock 42 40 40 Other equity securities 61 60 60 Total equity securities 103 100 100 Mortgage loans on real estate 4,401 4,401 Policy loans 1,358 1,358 Funds withheld at interest 6,083 6,083 Short-term investments 93 93 Other invested assets 1,505 1,505 Total investments $ 48,824 $ 51,691 (1) Fixed maturity securities are classified as available-for-sale and carried at fair value. (2) Includes fixed maturities directly issued by foreign governments, supranational and foreign government-sponsored enterprises.

Condensed Financial Information

Condensed Financial Information of The Registrant	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Financial Information of The Registrant	REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE II—CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT December 31, (dollars in thousands) 2017 2016 2015 CONDENSED BALANCE SHEETS Assets: Fixed maturity securities available-for-sale, at fair value $ 710,303 $ 1,154,559 Short-term and other investments 54,517 245,478 Cash and cash equivalents 15,176 43,718 Investment in subsidiaries 12,043,911 9,209,700 Loans to subsidiaries 1,010,000 1,050,000 Other assets 234,707 258,379 Total assets $ 14,068,614 $ 11,961,834 Liabilities and stockholders’ equity: Long-term debt - unaffiliated (1) $ 2,775,579 $ 3,073,249 Long-term debt - affiliated (2) 500,000 500,000 Other liabilities 1,223,500 1,295,503 Stockholders’ equity 9,569,535 7,093,082 Total liabilities and stockholders’ equity $ 14,068,614 $ 11,961,834 CONDENSED STATEMENTS OF INCOME Interest / dividend income (3) $ 131,067 $ 602,830 $ 321,645 Investment related gains (losses), net (5,187 ) 203 (324 ) Operating expenses (20,517 ) (20,742 ) (13,652 ) Interest expense (177,417 ) (168,924 ) (176,364 ) Income (loss) before income tax and undistributed earnings of subsidiaries (72,054 ) 413,367 131,305 Income tax expense (benefit) 65,882 (23,911 ) (19,465 ) Net income (loss) before undistributed earnings of subsidiaries (137,936 ) 437,278 150,770 Equity in undistributed earnings of subsidiaries 1,960,117 264,165 351,396 Net income 1,822,181 701,443 502,166 Other comprehensive income (loss) (7,672 ) 5,531 44,073 Total comprehensive income $ 1,814,509 $ 706,974 $ 546,239 The condensed financial information of RGA (the “Parent Company”) should be read in conjunction with the consolidated financial statements of RGA and its subsidiaries and the notes thereto (the “Consolidated Financial Statements”). These condensed unconsolidated financial statements reflect the results of operations, financial position and cash flows for RGA. Investments in subsidiaries are accounted for using the equity method of accounting. (1) Long-term debt - unaffiliated consists of the following: 2017 2016 $300 million 5.625% Senior Notes due 2017 $ — $ 299,945 $400 million 6.45% Senior Notes due 2019 399,873 399,805 $400 million 5.00% Senior Notes due 2021 399,245 399,025 $400 million 4.70% Senior Notes due 2023 399,138 398,986 $400 million 3.95% Senior Notes due 2026 399,987 399,985 $400 million 6.20% Subordinated Debentures due 2042 400,000 400,000 $400 million 5.75% Subordinated Debentures due 2056 400,000 400,000 $400 million Variable Rate Junior Subordinated Debentures due 2065 398,670 398,667 Subtotal 2,796,913 3,096,413 Unamortized debt issue costs (21,334 ) (23,164 ) Total $ 2,775,579 $ 3,073,249 Repayments of long-term debt—unaffiliated due over the next five years total $400,000 in 2019 and $400,000 in 2021. (2) Long-term debt—affiliated in 2017 and 2016 and consists of $500,000 of subordinated debt issued to various operating subsidiaries. (3) Interest/Dividend income includes $478,602 and $196,445 of cash dividends received from consolidated subsidiaries in 2016 and 2015, respectively. In 2017 there were no cash dividends received from consolidated subsidiaries. REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE II—CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT (continued) December 31, (dollars in thousands) 2017 2016 2015 CONDENSED STATEMENTS OF CASH FLOWS Operating activities: Net income $ 1,822,181 $ 701,443 $ 502,166 Equity in earnings of subsidiaries (1,960,117 ) (264,165 ) (351,396 ) Other, net 57,677 (63,795 ) 486,159 Net cash (used in) provided by operating activities (80,259 ) 373,483 636,929 Investing activities: Sales of fixed maturity securities available-for-sale 514,508 228,383 100,734 Purchases of fixed maturity securities available-for-sale (75,000 ) (984,397 ) (52,698 ) Repayments/issuances of loans to subsidiaries 40,000 20,000 (10,000 ) Purchase of a business, net of cash acquired of $529 — — (3,701 ) Change in short-term investments — 102,508 (102,508 ) Change in other invested assets 125,506 (109,914 ) (7,542 ) Capital contributions to subsidiaries (62,500 ) (314,142 ) (103,832 ) Net cash (used in) provided by investing activities 542,514 (1,057,562 ) (179,547 ) Financing activities: Dividends to stockholders (117,291 ) (100,371 ) (93,381 ) Purchases of treasury stock (43,508 ) (122,916 ) (384,519 ) Exercise of stock options, net 7,292 15,321 11,151 Net change in cash collateral for loaned securities (37,290 ) 105,093 — Principal payments on debt (300,000 ) — — Proceeds from unaffiliated long-term debt issuance — 799,984 — Debt issuance costs — (8,766 ) — Net cash (used in) provided by financing activities (490,797 ) 688,345 (466,749 ) Net change in cash and cash equivalents (28,542 ) 4,266 (9,367 ) Cash and cash equivalents at beginning of year 43,718 39,452 48,819 Cash and cash equivalents at end of year $ 15,176 $ 43,718 $ 39,452 Supplementary information: Cash paid for interest $ 185,554 $ 169,860 $ 165,775 Cash paid for income taxes, net of refunds $ 8,248 $ 1,500 $ (120,680 )

Supplementary Insurance Informa

Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2017
Supplementary Insurance Information [Abstract]
Supplementary Insurance Information	REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE III—SUPPLEMENTARY INSURANCE INFORMATION (dollars in thousands) As of December 31, Deferred Policy Acquisition Costs Future Policy Benefits and Interest-Sensitive Contract Liabilities Other Policy Claims and Benefits Payable 2017 U.S. and Latin America operations: Traditional operations $ 1,818,572 $ 11,343,921 $ 1,814,018 Financial Solutions operations 405,623 15,127,529 17,876 Canada operations: Traditional operations 212,345 3,041,790 206,655 Financial Solutions operations — 27,908 1,040 Europe, Middle East and Africa operations: Traditional operations 229,150 1,075,786 882,744 Financial Solutions operations — 4,741,983 38,044 Asia Pacific operations: Traditional operations 552,947 1,611,633 2,017,920 Financial Solutions operations 21,187 1,118,012 6,885 Corporate and Other — 502,321 6,892 Total $ 3,239,824 $ 38,590,883 $ 4,992,074 2016 U.S. and Latin America operations: Traditional operations $ 1,818,211 $ 10,990,560 $ 1,659,473 Financial Solutions operations 582,031 13,074,231 20,352 Canada operations: Traditional operations 201,149 2,713,510 200,246 Financial Solutions operations — 29,531 4,599 Europe, Middle East and Africa operations: Traditional operations 206,837 913,351 740,218 Financial Solutions operations — 3,457,196 46,761 Asia Pacific operations: Traditional operations 512,123 1,288,642 1,563,707 Financial Solutions operations 18,254 641,614 19,643 Corporate and Other — 502,292 8,027 Total $ 3,338,605 $ 33,610,927 $ 4,263,026 REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE III—SUPPLEMENTARY INSURANCE INFORMATION (continued) (dollars in thousands) Year ended December 31, Premium Income Net Investment Income Policyholder Benefits and Interest Credited Amortization of DAC Other Operating Expenses 2017 U.S. and Latin America operations: Traditional operations $ 5,356,321 $ 728,073 $ 4,842,412 $ 191,725 $ 692,600 Financial Solutions operations 23,683 778,473 458,368 185,280 105,146 Canada operations: Traditional operations 901,976 189,018 757,912 12,426 212,964 Financial Solutions operations 38,229 5,115 29,639 — 2,656 Europe, Middle East and Africa operations: Traditional operations 1,301,640 55,511 1,096,211 20,570 174,808 Financial Solutions operations 163,720 123,258 153,874 — 33,683 Asia Pacific operations: Traditional operations 2,053,029 91,675 1,635,728 91,477 334,695 Financial Solutions operations 2,419 34,529 40,467 1,388 18,790 Corporate and Other 113 148,999 6,346 — 273,789 Total $ 9,841,130 $ 2,154,651 $ 9,020,957 $ 502,866 $ 1,849,131 2016 U.S. and Latin America operations: Traditional operations $ 5,249,571 $ 699,833 $ 4,717,850 $ 177,255 $ 698,762 Financial Solutions operations 24,349 631,097 333,107 133,501 90,458 Canada operations: Traditional operations 928,642 178,927 707,428 10,621 265,250 Financial Solutions operations 38,701 2,692 36,275 — 2,718 Europe, Middle East and Africa operations: Traditional operations 1,140,062 50,301 999,005 33,795 132,290 Financial Solutions operations 180,271 125,282 178,014 — 24,497 Asia Pacific operations: Traditional operations 1,681,505 83,049 1,345,951 24,597 286,674 Financial Solutions operations 5,428 23,648 37,976 1,423 19,920 Corporate and Other 342 117,057 2,460 — 217,738 Total $ 9,248,871 $ 1,911,886 $ 8,358,066 $ 381,192 $ 1,738,307 2015 U.S. and Latin America operations: Traditional operations $ 4,806,706 $ 636,779 $ 4,444,196 $ 131,439 $ 653,620 Financial Solutions operations 22,177 566,180 310,464 40,416 85,022 Canada operations: Traditional operations 838,894 182,621 670,477 11,299 217,061 Financial Solutions operations 37,969 1,436 29,251 — 1,881 Europe, Middle East and Africa operations: Traditional operations 1,121,540 51,370 979,225 39,164 123,943 Financial Solutions operations 171,830 73,432 161,917 — 16,304 Asia Pacific operations: Traditional operations 1,551,586 80,549 1,208,984 7,373 316,346 Financial Solutions operations 19,474 18,678 20,766 185 16,011 Corporate and Other 565 123,450 1,066 — 186,973 Total $ 8,570,741 $ 1,734,495 $ 7,826,346 $ 229,876 $ 1,617,161

Supplemental Schedule of Reinsu

Supplemental Schedule of Reinsurance	12 Months Ended
	Dec. 31, 2017
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Reinsurance	REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE IV—REINSURANCE (in millions) As of or for the Year ended December 31, Gross Amount Ceded to Other Companies Assumed from Other Companies Net Amounts Percentage of Amount Assumed to Net 2017 Life insurance in force $ 1,462 $ 205,529 $ 3,297,275 $ 3,093,208 106.6 % Premiums U.S. and Latin America operations: Traditional operations $ 30.5 $ 610.4 $ 5,936.2 $ 5,356.3 110.8 % Financial Solutions operations 4.3 — 19.4 23.7 81.9 Canada operations: Traditional operations — 38.1 940.1 902.0 104.2 Financial Solutions operations — — 38.2 38.2 100.0 Europe, Middle East and Africa operations: Traditional operations 26.6 34.9 1,310.0 1,301.7 100.6 Financial Solutions operations 0.2 125.0 288.5 163.7 176.2 Asia Pacific operations: Traditional operations — 54.5 2,107.5 2,053.0 102.7 Financial Solutions operations — — 2.4 2.4 100.0 Corporate and Other — — 0.1 0.1 100.0 Total $ 61.6 $ 862.9 $ 10,642.4 $ 9,841.1 108.1 2016 Life insurance in force $ 1,576 $ 214,727 $ 3,062,525 $ 2,849,374 107.5 % Premiums U.S. and Latin America operations: Traditional operations $ 31.6 $ 616.0 $ 5,834.0 $ 5,249.6 111.1 % Financial Solutions operations 1.6 40.2 63.0 24.4 258.2 Canada operations: Traditional operations — 36.5 965.1 928.6 103.9 Financial Solutions operations — — 38.7 38.7 100.0 Europe, Middle East and Africa operations: Traditional operations 24.1 30.9 1,146.9 1,140.1 100.6 Financial Solutions operations 0.3 84.4 264.4 180.3 146.6 Asia Pacific operations: Traditional operations — 50.3 1,731.8 1,681.5 103.0 Financial Solutions operations — — 5.4 5.4 100.0 Corporate and Other — — 0.3 0.3 100.0 Total $ 57.6 $ 858.3 $ 10,049.6 $ 9,248.9 108.7 2015 Life insurance in force $ 1,686 $ 222,388 $ 2,995,079 $ 2,774,377 108.0 % Premiums U.S. and Latin America operations: Traditional operations $ 29.4 $ 607.0 $ 5,384.3 $ 4,806.7 112.0 % Financial Solutions operations 2.9 38.8 58.1 22.2 261.7 Canada operations: Traditional operations — 42.3 881.2 838.9 105.0 Financial Solutions operations — — 38.0 38.0 100.0 Europe, Middle East and Africa operations: Traditional operations 10.7 25.5 1,136.3 1,121.5 101.3 Financial Solutions operations 0.1 89.1 260.8 171.8 151.8 Asia Pacific operations: Traditional operations — 41.0 1,592.6 1,551.6 102.6 Financial Solutions operations — — 19.5 19.5 100.0 Corporate and Other — — 0.5 0.5 100.0 Total $ 43.1 $ 843.7 $ 9,371.3 $ 8,570.7 109.3

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE V—VALUATION AND QUALIFYING ACCOUNTS (in millions) Additions Description Balance at Beginning of Period Charged to Costs and Expenses Charged to Other Accounts Deductions Balance at End of Period 2017 Valuation allowance for deferred income taxes $ 133.4 $ 88.5 $ 10.6 $ 5.6 $ 226.9 Valuation allowance for mortgage loans 7.7 1.7 — — 9.4 2016 Valuation allowance for deferred income taxes $ 127.1 $ 11.0 $ (4.7 ) $ — $ 133.4 Valuation allowance for mortgage loans 6.8 0.9 — — 7.7 2015 Valuation allowance for deferred income taxes $ 112.0 $ 23.7 $ (8.6 ) $ — $ 127.1 Valuation allowance for mortgage loans 6.5 0.3 — — 6.8

Summary of Significant Accoun34

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Consolidation and Basis of Presentation	Basis of Presentation The consolidated financial statements of the Company have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosures of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The most significant estimates include those used in determining deferred policy acquisition costs, premiums receivable, future policy benefits, incurred but not reported claims, income taxes, valuation of investments and investment impairments, and valuation of embedded derivatives. Actual results could differ materially from the estimates and assumptions used by management. The accompanying consolidated financial statements include the accounts of RGA and its subsidiaries, all of which are wholly owned, and any variable interest entities where the Company is the primary beneficiary. Entities in which the Company has significant influence over the operating and financing decisions but are not required to be consolidated are reported under the equity method of accounting. The Company evaluates variable interest entities in accordance with the general accounting principles for Consolidation . Intercompany balances and transactions have been eliminated. There were no subsequent events that would require disclosure or adjustments to the accompanying consolidated financial statements through the date the consolidated financial statements were issued.
Investments	Investments Fixed Maturity Securities Fixed maturity securities classified as available-for-sale are reported at fair value and are so classified based upon the possibility that such securities could be sold prior to maturity if that action enables the Company to execute its investment philosophy and appropriately match investment results to operating and liquidity needs. Unrealized gains and losses on fixed maturity securities classified as available-for-sale, less applicable deferred income taxes as well as related adjustments to deferred acquisition costs, if applicable, are reflected as a direct charge or credit to accumulated other comprehensive income (“AOCI”) in stockholders’ equity on the consolidated balance sheets. Investment income is recognized as it accrues or is legally due. Realized gains and losses on sales of investments are included in investment related gains (losses), net, as are credit impairments that are other-than-temporary in nature. The cost of investments sold is primarily determined based upon the specific identification method. Mortgage Loans on Real Estate Mortgage loans on real estate are carried at unpaid principal balances, net of any unamortized premium or discount and valuation allowances. Interest income is accrued on the principal amount of the mortgage loan based on its contractual interest rate. Amortization of premiums and discounts is recorded using the effective yield method. The Company accrues interest on loans until it is probable the Company will not receive interest or the loan is 90 days past due. Interest income, amortization of premiums, accretion of discounts and prepayment fees are reported in investment income, net of related expenses in the consolidated statements of income. A mortgage loan is considered to be impaired when, based on the current information and events, it is probable that the Company will be unable to collect all amounts due according to the contractual terms of the mortgage agreement. Although all available and applicable factors are considered in the Company’s analysis, loan-to-value and debt service coverage ratios are the most critical factors in determining impairment. Valuation allowances on mortgage loans are established based upon inherent losses expected by management to be realized in connection with future dispositions or settlement of mortgage loans, including foreclosures. The Company establishes valuation allowances for estimated impairments on an individual loan basis as of the balance sheet date. Such valuation allowances are based on the excess carrying value of the loan over the present value of expected future cash flows discounted at the loan’s original effective interest rate, the value of the loan’s collateral if the loan is in the process of foreclosure or is otherwise collateral-dependent, or the loan’s market value if the loan is being sold. Non-specific valuation allowances are established for mortgage loans based upon several loan factors, including the Company’s historical experience for loan losses, defaults and loss severity, loss expectations for loans with similar risk characteristics and industry statistics. These evaluations are revised as conditions change and new information becomes available. In addition to historical experience, management considers qualitative factors that include the impact of changing macro-economic conditions, which may not be currently reflected in the loan portfolio performance, and the quality of the loan portfolio. Any interest accrued or received on the net carrying amount of the impaired loan will be included in investment income or applied to the principal of the loan, depending on the assessment of the collectability of the loan. Mortgage loans deemed to be uncollectible or that have been foreclosed are charged off against the valuation allowances and subsequent recoveries, if any, are credited to the valuation allowances. Changes in valuation allowances are reported in investment related gains (losses), net on the consolidated statements of income. The Company evaluates whether a mortgage loan modification represents a troubled debt restructuring. In a troubled debt restructuring, the Company grants concessions related to the borrower’s financial difficulties. Generally, the types of concessions include: reduction of the contractual interest rate, extension of the maturity date at an interest rate lower than current market interest rates and/or a reduction of accrued interest. The Company considers the amount, timing and extent of the concession granted in determining any impairment or changes in the specific valuation allowance recorded in connection with the troubled debt restructuring. Through the continuous monitoring process, the Company may have recorded a specific valuation allowance prior to when the mortgage loan is modified in a troubled debt restructuring. Accordingly, the carrying value (after specific valuation allowance) before and after modification through a troubled debt restructuring may not change significantly, or may increase if the expected recovery is higher than the pre-modification recovery assessment.
Policy Loans Receivable	Policy Loans Policy loans are reported at the unpaid principal balance. Interest income on such loans is recorded as earned using the contractually agreed-upon interest rate. These policy loans present no credit risk because the amount of the loan cannot exceed the obligation due the ceding company upon the death of the insured or surrender of the underlying policy. Funds Withheld at Interest Funds withheld at interest represent amounts contractually withheld by ceding companies in accordance with reinsurance agreements. For agreements written on a modified coinsurance basis and agreements written on a coinsurance funds withheld basis, assets which support the net statutory reserves or as defined in the treaty, are withheld and legally owned by the ceding company. Interest, recorded in investment income, net of related expenses in the consolidated statements of income, accrues to these assets at calculated rates as defined by the treaty terms. Changes in the value of the equity options held within the funds withheld portfolio associated with equity-indexed annuity treaties are reflected in investment income, net of related expenses. Short-term Investments Short-term investments represent investments with remaining maturities greater than three months but less than twelve months, at the date of purchase, and are stated at estimated fair value or amortized cost, which approximates estimated fair value. Interest on short-term investments is recorded in investment income, net of related expenses in the consolidated statements of income. Other Invested Assets In addition to derivative contracts discussed below, other invested assets include equity securities, contractholder-directed investments, limited partnership interests, joint ventures (other than operating joint ventures), equity release mortgages and structured loans. Equity securities are carried at fair value with the exception of the Company’s investment in the Federal Home Loan Bank of Des Moines (“FHLB”) common stock, which is carried at cost. The fair value option (“FVO”) was elected for contractholder-directed investments supporting unit-linked variable annuity type liabilities which do not qualify for presentation and reporting as separate accounts. Changes in estimated fair value of these securities are included in investment income, net of related expenses. Limited partnership interests and structured loans are primarily carried at cost. Based on the nature and structure of these investments, they do not meet the characteristics of an equity security in accordance with applicable accounting standards. Joint ventures and certain limited partnerships are reported using the equity method of accounting. Equity release mortgages are carried at unpaid principal balances, net of any unamortized premium or discount and valuation allowance. Interest income is accrued on the principal amount of the equity release mortgage based on its contractual interest rate. Securities Borrowing, Lending and Repurchase Agreements The Company participates in securities borrowing programs whereby securities, which are not reflected on the Company’s consolidated balance sheets, are borrowed from third parties. The borrowed securities are used to provide collateral under affiliated reinsurance transactions. The Company is required to maintain a minimum of 100% of the fair value, or par value under certain programs, of the borrowed securities as collateral. The collateral consists of rights to reinsurance treaty cash flows. If cash flows from the reinsurance treaties are insufficient to maintain the minimum collateral requirement, the Company may substitute cash or securities to meet the requirement. The Company participates in a securities lending program whereby securities, reflected as investments on the Company’s consolidated balance sheets, are loaned to a third party. The Company receives securities as collateral, in an amount equal to a minimum of 105% of the fair value of the securities lent. The securities received as collateral are not reflected on the Company’s consolidated balance sheets. The Company participates in a repurchase program in which securities, reflected as investments on the Company’s consolidated balance sheets, are pledged to a third party. In return, the Company receives cash from the third party, which is reflected as a payable to a third party, included in other liabilities on the consolidated balance sheets. The Company is required to maintain a minimum collateral balance with a fair value of 102% of the cash received. The Company participates in repurchase/reverse repurchase programs in which securities, reflected as investments on the Company’s consolidated balance sheets, are pledged to third parties. In return, the Company receives securities from the third parties with an estimated fair value equal to a minimum of 100% of the securities pledged. The securities received are not reflected on the Company’s consolidated balance sheets. Other-than-Temporary Impairment The Company identifies fixed maturity and equity securities that could potentially have credit impairments that are other-than-temporary by monitoring market events that could impact issuers’ credit ratings, business climates, management changes, litigation, government actions and other similar factors. The Company also monitors late payments, pricing levels, rating agency actions, key financial ratios, financial statements, revenue forecasts and cash flow projections as indicators of credit issues. The Company reviews all securities on a case-by-case basis to determine whether an other-than-temporary decline in value exists and whether losses should be recognized. The Company considers relevant facts and circumstances in evaluating whether a credit or interest rate-related impairment of a security is other-than-temporary. Relevant facts and circumstances considered include: (1) the extent and length of time the fair value has been below cost; (2) the reasons for the decline in fair value; (3) the issuers financial position and access to capital; and (4) for fixed maturity securities, the Company’s intent to sell a security or whether it is more likely than not it will be required to sell the security before the recovery of its amortized cost which, in some cases, may extend to maturity and for equity securities, the Company’s ability and intent to hold the security for a period of time that allows for the recovery in value. To the extent the Company determines that a security is deemed to be other-than-temporarily impaired, an impairment loss is recognized. Impairment losses on equity securities are reported in investment related gains (losses), net on the consolidated statements of income. Impairment losses on fixed maturity securities recognized in the financial statements are dependent on the facts and circumstances related to the specific security. If the Company intends to sell a security or it is more likely than not that it would be required to sell a security before the recovery of its amortized cost, less any recorded credit loss, it recognizes an other-than-temporary impairment in investment related gains (losses), net on the consolidated statements of income for the difference between amortized cost and fair value. If neither of these two conditions exists then the recognition of the other-than-temporary impairment is bifurcated and the Company recognizes the credit loss portion in investment related gains (losses), net and the non-credit loss portion in AOCI. The Company estimates the amount of the credit loss component of a fixed maturity security impairment as the difference between amortized cost and the present value of the expected cash flows of the security. The present value is determined using the best estimate cash flows discounted at the effective interest rate implicit to the security at the date of purchase or the current yield to accrete an asset-backed or floating rate security. The techniques and assumptions for establishing the best estimate cash flows vary depending on the type of security. The asset-backed securities’ cash flow estimates are based on security-specific facts and circumstances that may include collateral characteristics, expectations of delinquency and default rates, loss severity and prepayment speeds and structural support, including subordination and guarantees. The corporate fixed maturity security cash flow estimates are derived from scenario-based outcomes of expected corporate restructurings or the disposition of assets using security specific facts and circumstances including timing, security interests and loss severity. In periods after an other-than-temporary impairment loss is recognized on a fixed maturity security, the Company will report the impaired security as if it had been purchased on the date it was impaired and will continue to estimate the present value of the estimated cash flows of the security. Accordingly, the discount (or reduced premium) based on the new cost basis is accreted into net investment income over the remaining term of the fixed maturity security in a prospective manner based on the amount and timing of estimated future cash flows. The Company considers its cost method investments for other-than-temporary impairment when the carrying value of these investments exceeds the net asset value. The Company takes into consideration the severity and duration of this excess when deciding if the cost method investment is other-than-temporarily impaired. For equity method investments (including real estate ventures), the Company considers financial and other information provided by the investee, other known information and inherent risks in the underlying investments, as well as future capital commitments, in determining whether an impairment has occurred.
Derivative Instruments	Derivative Instruments Overview The Company utilizes a variety of derivative instruments including swaps, options, forwards and futures, primarily to manage or hedge interest rate risk, credit risk, inflation risk, foreign currency risk, market volatility and various other market risks associated with its business. The Company does not invest in derivatives for speculative purposes. It is the Company’s policy to enter into derivative contracts primarily with highly rated parties. See Note 5 - “Derivative Instruments” for additional detail on the Company’s derivative positions. Accounting and Financial Statement Presentation of Derivatives Derivatives are carried on the Company’s consolidated balance sheets primarily in other invested assets or other liabilities, at fair value. Certain derivatives are subject to master netting provisions and reported as a net asset or liability. On the date a derivative contract is executed, the Company designates the derivative as (1) a fair value hedge, (2) a cash flow hedge, (3) a net investment hedge in a foreign operation or (4) free-standing derivatives held for other risk management purposes, which primarily involve managing asset or liability risks associated with the Company’s reinsurance treaties which do not qualify for hedge accounting. Changes in the fair value of free-standing derivative instruments, which do not receive accounting hedge treatment, are primarily reflected in investment related gains (losses), net. Changes in the fair value of non-investment free-standing derivative instruments (e.g. mortality and longevity swaps), which do not receive accounting hedge treatment, are reflected in other revenues. Hedge Documentation and Hedge Effectiveness To qualify for hedge accounting, at the inception of the hedging relationship, the Company formally documents its risk management objective and strategy for undertaking the hedging transaction, as well as its designation of the hedge as either (i) a fair value hedge; (ii) a cash flow hedge; or (iii) a hedge of a net investment in a foreign operation. In this documentation, the Company sets forth how the hedging instrument is expected to hedge the designated risks related to the hedged item and sets forth the method that will be used to retrospectively and prospectively assess the hedging instrument’s effectiveness and the method which will be used to measure ineffectiveness. A derivative designated as a hedging instrument must be assessed as being highly effective in offsetting the designated risk of the hedged item. Hedge effectiveness is formally assessed at inception and periodically throughout the life of the designated hedging relationship. Under a fair value hedge, changes in the fair value of the hedging derivative, including amounts measured as ineffective, and changes in the fair value of the hedged item related to the designated risk being hedged, are reported within investment related gains (losses), net. The fair values of the hedging derivatives are exclusive of any accruals that are separately reported in the consolidated statement of income within interest income or interest expense to match the location of the hedged item. Under a cash flow hedge, changes in the fair value of the hedging derivative measured as effective are reported within AOCI and the deferred gains or losses on the derivative are reclassified into the consolidated statement of income when the Company’s earnings are affected by the variability in cash flows of the hedged item. Changes in the fair value of the hedging instrument measured as ineffective are reported within investment related gains (losses), net. The fair values of the hedging derivatives are exclusive of any accruals that are separately reported in the consolidated statement of income within interest income or interest expense to match the location of the hedged item. In a hedge of a net investment in a foreign operation, changes in the fair value of the hedging derivative that are measured as effective are reported within AOCI consistent with the translation adjustment for the hedged net investment in the foreign operation. Changes in the fair value of the hedging instrument measured as ineffective are reported within investment related gains (losses), net. The Company discontinues hedge accounting prospectively when: (i) it is determined that the derivative is no longer highly effective in offsetting changes in the estimated fair value or cash flows of a hedged item; (ii) the derivative expires, is sold, terminated, or exercised; (iii) it is no longer probable that the hedged forecasted transaction will occur; or (iv) the derivative is de-designated as a hedging instrument. When hedge accounting is discontinued because it is determined that the derivative is not highly effective, the derivative continues to be carried in the consolidated balance sheets at fair value, with changes in fair value recognized in investment related gains (losses), net. The carrying value of the hedged asset or liability under a fair value hedge is no longer adjusted for changes in its estimated fair value due to the hedged risk, and the cumulative adjustment to its carrying value is amortized into income over the remaining life of the hedged item. Provided the hedged forecasted transaction occurrence is still probable, the changes in estimated fair value of derivatives recorded in other comprehensive income (loss) (“OCI”) related to discontinued cash flow hedges are released into the consolidated statement of income when the Company’s earnings are affected by the variability in cash flows of the hedged item. When hedge accounting is discontinued because it is no longer probable that the forecasted transactions will occur on the anticipated date or within two months of that date, the derivative continues to be carried in the consolidated balance sheets at its estimated fair value, with changes in estimated fair value recognized currently in investment related gains (losses), net. Deferred gains and losses of a derivative recorded in OCI pursuant to the discontinued cash flow hedge of a forecasted transaction that is no longer probable are recognized immediately in investment related gains (losses), net. In all other situations in which hedge accounting is discontinued, the derivative is carried at its estimated fair value in the consolidated balance sheets, with changes in its estimated fair value recognized in the current period as investment related gains (losses), net. Embedded Derivatives The Company reinsures certain annuity products that contain terms that are deemed to be embedded derivatives, primarily equity-indexed annuities and variable annuities with guaranteed minimum benefits. The Company assesses reinsurance contract terms to identify embedded derivatives which are required to be bifurcated under the general accounting principles for Derivatives and Hedging . If the contract is not reported for in its entirety at fair value and it is determined that the terms of the embedded derivative are not clearly and closely related to the economic characteristics of the host contract, and that a separate instrument with the same terms would qualify as a derivative instrument, the embedded derivative is bifurcated from the host contract and accounted for separately. Such embedded derivatives are carried on the consolidated balance sheets at fair value in the same line item as the host contract. Changes in the fair value of embedded derivatives associated with equity-indexed annuities are reflected in interest credited on the consolidated statements of income and changes in the fair value of embedded derivatives associated with variable annuity guaranteed minimum benefits are reflected in investment related gains (losses), net on the consolidated statements of income. See “Interest-Sensitive Contract Liabilities” below for additional information on embedded derivatives related to equity-indexed and variable annuities. The Company has implemented an economic hedging strategy to mitigate the volatility associated with its reinsurance of variable annuity guaranteed minimum benefits. The hedging strategy is designed such that changes in the fair value of the hedge contracts, primarily futures, swap contracts and options, move in the opposite direction of changes in the fair value of the embedded derivatives. While the Company actively manages its hedging program, the hedges that are in place may not be totally effective in offsetting the embedded derivative changes due to the many variables that must be managed and the Company may see a corresponding increase or decrease in the net liability. The Company has elected not to assess this hedging strategy for hedge accounting treatment. Additionally, reinsurance treaties written on a modified coinsurance or funds withheld basis are subject to the general accounting principles for Derivatives and Hedging related to embedded derivatives. The Company’s funds withheld at interest balances are primarily associated with its reinsurance treaties structured on a modified coinsurance or funds withheld basis, the majority of which were subject to the general accounting principles for Derivatives and Hedging related to embedded derivatives. Management believes the embedded derivative feature in each of these reinsurance treaties is similar to a total return swap on the assets held by the ceding companies. The valuation of embedded derivatives is sensitive to the investment credit spread environment. Changes in investment credit spreads are also affected by the application of a credit valuation adjustment (“CVA”). The fair value calculation of an embedded derivative in an asset position utilizes a CVA based on the ceding company’s credit risk. Conversely, the fair value calculation of an embedded derivative in a liability position utilizes a CVA based on the Company’s credit risk. Generally, an increase in investment credit spreads, ignoring changes in the CVA, will have a negative impact on the fair value of the embedded derivative (decrease in income). The fair value of the embedded derivatives is included in the funds withheld at interest line item on the consolidated balance sheets. The change in the fair value of the embedded derivatives is recorded in investment related gains (losses), net on the consolidated statements of income. The Company has entered into various financial reinsurance treaties on a funds withheld and modified coinsurance basis. These treaties do not transfer significant insurance risk and are recorded on a deposit method of accounting with the Company earning a net fee. As a result of the experience refund provisions contained in these treaties, the value of the embedded derivatives in these contracts is currently considered immaterial. The Company monitors the performance of these treaties on a quarterly basis. Significant adverse performance or losses on these treaties may result in a loss associated with the embedded derivative.
Fair Value Measurements	Fair Value Measurements General accounting principles for Fair Value Measurements and Disclosures define fair value, establish a framework for measuring fair value, establish a fair value hierarchy based on the inputs used to measure fair value and enhance disclosure requirements for fair value measurements. In compliance with these principles, the Company has categorized its assets and liabilities, based on the priority of the inputs to the valuation technique, into a three level hierarchy or separately for assets measured using the net asset value (“NAV”). The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1), the second highest priority to quoted prices in markets that are not active or inputs that are observable either directly or indirectly (Level 2) and the lowest priority to unobservable inputs (Level 3). If the inputs used to measure fair value fall within different levels of the hierarchy, the category level is based on the lowest priority level input that is significant to the fair value measurement of the asset or liability. See Note 6 - “Fair Value of Assets and Liabilities” for further details on the Company’s assets and liabilities recorded at fair value.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash on deposit and highly liquid debt instruments purchased with an original maturity of three months or less.
Premiums Receivable	Premiums Receivable Premiums are accrued when due and in accordance with information received from the ceding company. When the Company enters into a new reinsurance agreement, it records accruals based on the terms of the reinsurance treaty. Similarly, when a ceding company fails to report information on a timely basis, the Company records accruals based on the terms of the reinsurance treaty as well as historical experience. Other management estimates include adjustments for increased in force on existing treaties, lapsed premiums given historical experience, the financial health of specific ceding companies, collateral value and the legal right of offset on related amounts (i.e. allowances and claims) owed to the ceding company. Under the legal right of offset provisions in its reinsurance treaties, the Company can withhold payments for allowances and claims from unpaid premiums. Based on its review of these factors and historical experience, the Company did not believe a provision for doubtful accounts was necessary as of December 31, 2017 or 2016 .
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs Costs of acquiring new business, which vary with and are directly related to the production of new business, have been deferred to the extent that such costs are deemed recoverable from future premiums or gross profits. Such costs include commissions and allowances as well as certain costs of policy issuance and underwriting. Non-commission costs related to the acquisition of new and renewal insurance contracts may be deferred only if they meet the following criteria: • Incremental direct costs of a successful contract acquisition • Portions of employees’ salaries and benefits directly related to time spent performing specified acquisition activities for a contract that has been acquired or renewed • Other costs directly related to the specified acquisition or renewal activities that would not have been incurred had that acquisition contract transaction not occurred The Company tests the recoverability for each year of business at issue before establishing additional deferred acquisition costs (“DAC”). The Company also performs annual tests to establish that DAC are expected to remain recoverable, and if financial performance significantly deteriorates to the point where a deficiency exists, a cumulative charge to current operations will be recorded. No such adjustments related to DAC recoverability were made in 2017, 2016 and 2015 . DAC related to traditional life insurance contracts are amortized with interest over the premium-paying period of the related policies in proportion to the ratio of individual period premium revenues to total anticipated premium revenues over the life of the policy. Such anticipated premium revenues are estimated using the same assumptions used for computing liabilities for future policy benefits. DAC related to interest-sensitive life and investment-type policies are amortized over the lives of the policies, in proportion to the gross profits realized from mortality, investment income less interest credited, and expense margins.
Other Reinsurance Balances	Other Reinsurance Balances The Company assumes and retrocedes financial reinsurance contracts that do not expose it to a reasonable possibility of loss from insurance risk. These contracts are reported as deposits and are included in other reinsurance assets/liabilities. The amount of revenue reported in other revenues on these contracts represents fees and the cost of insurance under the terms of the reinsurance agreement. Assets and liabilities are reported on a net or gross basis, depending on the specific details within each treaty. Reinsurance agreements reported on a net basis, where a legal right of offset exists, are generally included in other reinsurance balances on the consolidated balance sheets. Balances resulting from the assumption and/or subsequent transfer of benefits and obligations resulting from cash flows related to variable annuities have also been classified as other reinsurance balance assets and/or liabilities. Other reinsurance assets are included in premiums receivable and other reinsurance balances while other reinsurance liabilities are included in other reinsurance balances on the consolidated balance sheets.
Goodwill and Value of Business Acquired	Goodwill and Value of Business Acquired Goodwill, reported in other assets, is not amortized into results of operations, but instead is reviewed at least annually for impairment and written down only in the periods in which the recorded value of goodwill exceeds its fair value. Goodwill as of December 31, 2017 and 2016 totaled $7.0 million . The value of business acquired (“VOBA”) is amortized in proportion to the ratio of annual premium revenues to total anticipated premium revenues or in relation to the present value of estimated profits. Anticipated premium revenues have been estimated using assumptions consistent with those used in estimating reserves for future policy benefits. The carrying value is reviewed at least annually for indicators of impairment in value. The VOBA was approximately $3.3 million and $3.1 million , including accumulated amortization of $14.6 million and $14.3 million , as of December 31, 2017 and 2016 , respectively. The VOBA amortization expense for the years ended December 31, 2017, 2016 and 2015 was $0.3 million , $0.5 million , and $0.4 million , respectively. These amortized balances are included in other assets on the consolidated balance sheets. Future amortization of the VOBA is not material.
Value of Distribution Agreements and Customer Relationships Acquired	Value of Distribution Agreements and Customer Relationships Acquired Value of distribution agreements (“VODA”) is reported in other assets and represents the present value of future profits associated with the expected future business derived from the distribution agreements. Value of customer relationships acquired (“VOCRA”) is also reported in other assets and represents the present value of the expected future profits associated with the expected future business acquired through existing customers of the acquired company or business. The VODA is amortized over a useful life of 15 years and the VOCRA is also amortized over a 15 year period in proportion to expected revenues generated. Such amortization is included in policy acquisition costs and other insurance expenses for reinsurance-related acquisitions or other operating expenses for other acquisitions. Each year the Company reviews VODA and VOCRA to determine the recoverability of these balances. VODA and VOCRA totaled approximately $52.3 million and $61.2 million , including accumulated amortization of $72.1 million and $63.2 million , as of December 31, 2017 and 2016 , respectively. The VODA and VOCRA amortization expense for the years ended December 31, 2017, 2016 and 2015 was $8.9 million , $9.3 million and $9.5 million , respectively. Amortization of the VODA and VOCRA is estimated to be $8.6 million , $8.3 million , $7.8 million , $6.9 million and $6.6 million during 2018, 2019, 2020, 2021 and 2022, respectively.
Other Assets	Property, equipment and leasehold improvements, which are included in other assets, are stated at cost, less accumulated depreciation. Depreciation is determined using the straight-line method over the estimated useful lives of the assets, as appropriate. The estimated life is generally 40 years for company occupied real estate property, from one to seven years for leasehold improvements, and from three to seven years for all other property and equipment. The cost basis of the property, equipment and leasehold improvements was $236.1 million and $221.7 million at December 31, 2017 and 2016 , respectively. Accumulated depreciation of property, equipment and leasehold improvements was $79.4 million and $60.8 million at December 31, 2017 and 2016 , respectively. Related depreciation expense was $17.2 million , $16.6 million and $17.1 million for the years ended December 31, 2017, 2016 and 2015 , respectively. The Company had assets acquired under capital leases, included in the total above, of $136.3 million and $145.7 million , net of accumulated depreciation of $30.5 million and $21.0 million as of December 31, 2017 and 2016 , respectively. Depreciation on assets under capital leases charged to expense is included in other operating expenses. Depreciation expense for the years ended December 31, 2017, 2016 and 2015 was $9.4 million , $9.6 million and $10.0 million , respectively. Computer software, which is included in other assets, is stated at cost, less accumulated amortization. Purchased software costs, as well as certain internal and external costs incurred to develop internal-use computer software during the application development stage, are capitalized. Amortization of software costs is recorded on a straight-line basis over periods ranging from three to ten years. Carrying values are reviewed periodically for indicators of impairment in value. Unamortized computer software costs were $145.5 million and $139.8 million at December 31, 2017 and 2016 , respectively. Amortization expense was $35.7 million , $10.3 million , and $14.0 million for the years ended December 31, 2017, 2016 and 2015 , respectively. The Company recognized capital project write-offs of $24.5 million , $0.6 million and $6.0 million in 2017, 2016 and 2015 , respectively.
Future Policy Benefits	Future Policy Benefits Liabilities for future benefits on life policies are established in an amount adequate to meet the estimated future obligations on policies in force. Liabilities for future policy benefits under long-term life insurance policies have been computed based upon expected investment yields, mortality and withdrawal (lapse) rates, and other assumptions. These assumptions include a margin for adverse deviation and vary with the characteristics of the plan of insurance, year of issue, age of insured, and other appropriate factors. Interest rates range from 3.0% to 6.0% . The mortality and withdrawal assumptions are based on the Company’s experience as well as industry experience and standards. In establishing reserves for future policy benefits, the Company assigns policy liability assumptions to particular timeframes (eras) in such a manner as to be consistent with the underlying assumptions and economic conditions at the time the risks are assumed. The Company maintains a consistent approach to setting the provision for adverse deviation between eras. Liabilities for future benefits on longevity business, including annuities in the payout phase, are established in an amount adequate to meet the estimated future obligations on policies in force. Liabilities for future benefits related to the longevity business, including annuities in the payout phase have been calculated using expected mortality, investment yields, and other assumptions. These assumptions include a margin for adverse deviation and vary with the characteristics of the plan of insurance, year of issue, age of insured, and other appropriate factors. The mortality assumptions are based on the Company’s experience as well as industry experience and standards. A deferred profit liability is established when the gross premium exceeds the net premium. The Company periodically reviews actual and anticipated experience compared to the assumptions used to establish policy benefits. The Company establishes premium deficiency reserves if actual and anticipated experience indicates that existing policy liabilities together with the present value of future gross premiums will not be sufficient to cover the present value of future benefits, settlement and maintenance costs and to recover unamortized acquisition costs. Anticipated investment income is considered in the calculation of premium deficiency losses for short duration contracts. The premium deficiency reserve is established by a charge to income, as well as a reduction in unamortized acquisition costs and, to the extent there are no unamortized acquisition costs, an increase in future policy benefits. The reserving process includes normal periodic reviews of assumptions used and adjustments of reserves to incorporate the refinement of the assumptions. Any such adjustments relate only to policies assumed in recent periods and the adjustments are reflected by a cumulative charge or credit to current operations. The Company reinsures disability products in various markets. Liabilities for future benefits on disability policies’ active lives are established in an amount adequate to meet the estimated future obligations on policies in force. These reserves are the amounts which, with the additional premiums to be received and interest thereon compounded annually at certain assumed rates, are calculated to be sufficient to meet the various policy and contract obligations as they mature. The Company establishes future policy benefits for guaranteed minimum death benefits (“GMDB”) relating to the reinsurance of certain variable annuity contracts by estimating the expected value of death benefits in excess of the projected account balance and recognizing the excess proportionally over the accumulation period based on total expected assessments. The Company regularly evaluates estimates used and adjusts the additional liability balance, with a related charge or credit to claims and other policy benefits, if actual experience or other evidence suggests that earlier assumptions should be revised. The assumptions used in estimating the GMDB liabilities are consistent with those used for amortizing DAC, and are thus subject to the same variability and risk. The Company’s GMDB liabilities at December 31, 2017 and 2016 were not material.
Interest-Sensitive Contract Liabilities	Interest-Sensitive Contract Liabilities Liabilities for future benefits on interest-sensitive life and investment-type contract liabilities are carried at the accumulated contract holder values without reduction for potential surrender or withdrawal charges. The Company reinsures asset-intensive products, including annuities and corporate-owned life insurance. The investment portfolios for these products are segregated for management purposes within the general account of RGA Reinsurance Company (“RGA Reinsurance”). The liabilities under asset-intensive insurance contracts or reinsurance contracts reinsured on a coinsurance basis are included in interest-sensitive contract liabilities on the consolidated balance sheets. Asset-intensive contracts principally include individual fixed annuities in the accumulation phase, single premium immediate annuities, equity-indexed annuities, individual variable annuities, corporate-owned life and interest-sensitive whole life insurance contracts. Interest-sensitive contract liabilities are equal to (i) policy account values, which consist of an accumulation of gross premium payments; (ii) credited interest less expenses, mortality charges, and withdrawals; and (iii) fair value adjustments relating to business combinations. Liabilities for immediate annuities are calculated as the present value of the expected cash flows, with the locked-in discount rate determined such that there is no gain or loss at inception. Additionally, certain annuity contracts the Company reinsures contain terms, such as guaranteed minimum benefits and equity participation options, which are deemed to be embedded derivatives and are accounted for based on the general accounting principles for Derivatives and Hedging . The Company establishes liabilities for guaranteed minimum living benefits relating to certain variable annuity products as follows: Guaranteed minimum income benefits (“GMIB”) provide the contract holder, after a specified period of time determined at the time of issuance of the variable annuity contract, with a minimum level of income (annuity) payments. Under the reinsurance treaty, the Company makes a payment to the ceding company equal to the GMIB net amount-at-risk at the time of annuitization and thus these contracts meet the net settlement criteria of the general accounting principles for Derivatives and Hedging and the Company assumes no mortality risk. Accordingly, the GMIB is considered an embedded derivative, which is measured at fair value separately from the host variable annuity product. Guaranteed minimum withdrawal benefits (“GMWB”) guarantee the contract holder a return of their purchase payment via partial withdrawals, even if the account value is reduced to zero, provided that the contract holder’s cumulative withdrawals in a contract year do not exceed a certain limit. The initial guaranteed withdrawal amount is equal to the initial benefit base as defined in the contract (typically, the initial purchase payments plus applicable bonus amounts). The GMWB is also an embedded derivative, which is measured at fair value separately from the host variable annuity product. Guaranteed minimum accumulation benefits (“GMAB”) provide the contract holder, after a specified period of time determined at the time of issuance of the variable annuity contract, with a minimum accumulation of their purchase payments even if the account value is reduced to zero. The initial guaranteed accumulation amount is equal to the initial benefit base as defined in the contract (typically, the initial purchase payments plus applicable bonus amounts). The GMAB is also an embedded derivative, which is measured at fair value separately from the host variable annuity product. For GMIB, GMWB and GMAB, the initial benefit base is increased by additional purchase payments made within a certain time period and decreased by benefits paid and/or withdrawal amounts. After a specified period of time, the benefit base may also increase as a result of an optional reset as defined in the contract. The fair values of the GMIB, GMWB and GMAB embedded derivative liabilities are reflected in interest-sensitive contract liabilities on the consolidated balance sheets and are calculated based on actuarial and capital market assumptions related to the projected cash flows, including benefits and related contract charges over the lives of the contracts. These projected cash flows incorporate expectations concerning policyholder behavior, such as lapses, withdrawals and benefit selections, and capital market assumptions such as interest rates and equity market volatilities. In measuring the fair value of GMIBs, GMWBs and GMABs, the Company attributes a portion of the fees collected from the policyholder equal to the present value of expected future guaranteed minimum income, withdrawal and accumulation benefits (at inception). The changes in fair value are reported in investment related gains (losses), net. Any additional fees represent “excess” fees and are reported in other revenues on the consolidated statements of income. These variable annuity guaranteed living benefits may be more costly than expected in volatile or declining equity markets or falling interest rate markets, causing an increase in interest-sensitive contract liabilities, negatively affecting net income. The Company reinsures equity-indexed annuity contracts. These contracts allow the contract holder to elect an interest rate return or an equity market component where interest credited is based on the performance of common stock market indices, such as the S&P 500 Index ® , the Dow Jones Industrial Average, or the NASDAQ. The equity market option is considered an embedded derivative, similar to a call option, which is reflected at fair value on the consolidated balance sheets in interest-sensitive contract liabilities. The fair value of embedded derivatives is computed based on a projection of future equity option costs using a budget methodology, discounted back to the balance sheet date using current market indicators of volatility and interest rates. Changes in the fair value of the embedded derivatives are included as a component of interest credited on the consolidated statements of income. The Company reviews its estimates of actuarial liabilities for interest-sensitive contract liabilities and compares them with its actual experience. Differences between actual experience and the assumptions used in pricing these guarantees and benefits and in the establishment of the related liabilities result in variances in profit and could result in losses. The effects of changes in such estimated liabilities are included in the results of operations in the period in which the changes occur.
Other Policy Claims and Benefits	Other Policy Claims and Benefits Claims payable for incurred but not reported losses are determined using case-basis estimates and lag studies of past experience. The time lag from the date of the claim or death to when the ceding company reports the claim to the Company can vary significantly by ceding company, business segment and product type, but generally averages around 3.6 months. Incurred but not reported claims are estimates on an undiscounted basis, using actuarial estimates of historical claims expense, adjusted for current trends and conditions. These estimates are continually reviewed and the ultimate liability may vary significantly from the amount recognized, which are reflected in claims and other policy benefits in the consolidated statements of income in the period in which they are determined.
Other Liabilities	Other Liabilities Other liabilities primarily include investments in transit, separate accounts, employee benefits, cash collateral received on derivative positions and current federal income taxes payable.
Income Taxes	Income Taxes The U.S. consolidated tax return includes the operations of RGA and all eligible subsidiaries. Aurora National Life Assurance Company’s (“Aurora National”) files a separate U.S. income tax return as it is ineligible for inclusion in the consolidated federal tax return until 2021. The Company’s foreign subsidiaries are taxed under applicable local statutes. The Company provides for federal, state and foreign income taxes currently payable, as well as those deferred due to temporary differences between the financial reporting and tax bases of assets and liabilities and are recognized in net income or in certain cases in OCI. The Company’s accounting for income taxes represents management’s best estimate of various events and transactions considering the laws enacted as of the reporting date. The Tax Cuts and Jobs Act of 2017 (“U.S. Tax Reform”) creates additional complexity due to various provisions that require management judgment and assumptions, which are subject to change. Deferred tax assets and liabilities resulting from temporary differences between the financial reporting and tax bases of assets and liabilities are measured at the balance sheet date using enacted tax rates in the relevant jurisdictions expected to apply to taxable income in the years the temporary differences are expected to reverse. The realization of deferred tax assets depends upon the existence of sufficient taxable income within the carryback or carryforward periods under the tax law in the applicable tax jurisdiction. The Company has deferred tax assets related to net operating and capital losses. The Company has projected its ability to utilize its U.S. and foreign net operating losses and has determined that all of the U.S. losses are expected to be utilized prior to their expiration and established a valuation allowance on the portion of the foreign deferred tax assets the Company believes more likely than not that deferred income tax assets will not be realized. The Company also has deferred tax assets related to foreign tax credit (“FTC”) carryforwards. The Company established a valuation allowance on the FTC carryforwards as the Company no longer expects to realize these credits. The Company will establish a valuation allowance if management determines, based on available information, that it is more likely than not that deferred income tax assets will not be realized. Significant judgment is required in determining whether valuation allowances should be established as well as the amount of such allowances. When making such a determination, consideration is given to, among other things, the following: (i) future taxable income exclusive of reversing temporary differences and carryforwards; (ii) future reversals of existing taxable temporary differences; (iii) taxable income in prior carryback years; and (iv) tax planning strategies. Any such changes could significantly affect the amounts reported in the consolidated financial statements in the year these changes occur. The Company reports its total liability for uncertain tax positions considering the recognition and measurement thresholds established in general accounting principles for income taxes. The tax effects of a position are recognized in the consolidated statement of income only if it is more likely than not to be sustained upon examination by the appropriate taxing authority. Unrecognized tax benefits due to tax uncertainties that do not meet the more likely than not criteria are included within other liabilities and are charged to earnings in the period that such determination is made. The Company classifies interest related to tax uncertainties as interest expense whereas penalties related to tax uncertainties are classified as a component of income tax.
Collateral Finance Facility	Collateral Finance and Securitization Notes Collateral finance and securitization notes represent private placement asset-backed structured financing transactions. Collateral finance notes are issued on specified insurance policies reinsured by the Company’s regulated subsidiaries. Transaction costs, primarily interest expense, are reflected in collateral finance and securitization expense. See Note 14 - “Collateral Finance and Securitization Notes” for additional information.
Foreign Currency Translation	Foreign Currency Translation Assets, liabilities and results of foreign operations are recorded based on the functional currency of each foreign operation. The determination of the functional currency is based on economic facts and circumstances pertaining to each foreign operation. The Company’s material functional currencies are the U.S. dollar, Canadian dollar, British pound, Australian dollar, Japanese yen, Korean won, Euro and South African rand. The translation of the functional currency into U.S. dollars is performed for balance sheet accounts using current exchange rates in effect at the balance sheet date and for revenue and expense accounts using weighted-average exchange rates during each year. Gains or losses, net of applicable deferred income taxes, resulting from such translation are included in accumulated currency translation adjustments, in AOCI on the consolidated balance sheets until the underlying functional currency operation is sold or substantially liquidated.
Recognition of Revenues and Related Expenses	Recognition of Revenues and Related Expenses Life and health premiums are recognized as revenue when due from the insured, and are reported net of amounts retroceded. Benefits and expenses are reported net of amounts retroceded and are associated with earned premiums so that profits are recognized over the life of the related contract. This association is accomplished through the provision for future policy benefits and the amortization of deferred policy acquisition costs. Other revenue includes items such as treaty recapture fees, fees associated with financial reinsurance and policy changes on interest-sensitive and investment-type products that the Company reinsures. Any fees that are collected in advance of the period benefited are deferred and recognized over the period benefited. For certain reinsurance transactions involving in force blocks of business, the ceding company pays a premium equal to the initial required reserve (future policy benefit). In such transactions, for income statement presentation, the Company nets the expense associated with the establishment of the reserve on the consolidated balance sheets against the premiums from the transaction. Revenues for interest-sensitive and investment-type products consist of investment income, policy charges for the cost of insurance, policy administration, and surrenders that have been assessed against policy account balances during the period. Interest-sensitive contract liabilities for these products represent policy account balances before applicable surrender charges. Policy benefits and claims that are charged to expenses include claims incurred in the period in excess of related policy account balances and interest credited to policy account balances. Interest is credited to policyholder account balances according to terms of the policies or contracts. For each of its reinsurance contracts, the Company must determine if the contract provides indemnification against loss or liability relating to insurance risk, in accordance with GAAP. The Company must review all contractual features, particularly those that may limit the amount of insurance risk to which the Company is subject or features that delay the timely reimbursement of claims. If the Company determines that a contract does not expose it to a reasonable possibility of a significant loss from insurance risk, the Company records the contract on a deposit method of accounting with any net amount receivable reflected as an asset within premiums receivable and other reinsurance balances, and any net amount payable reflected as a liability within other reinsurance balances on the consolidated balance sheets. Fees earned on the contracts are reflected as other revenues, rather than premiums, on the consolidated statements of income.
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	Equity Based Compensation The Company expenses the fair value of stock awards included in its incentive compensation plans. As of the date stock awards are approved, the fair value of stock options is determined using a Black-Scholes options valuation methodology, and the fair value of other stock awards is based upon the market value of the stock on the grant date. The fair value of the awards is expensed over the performance or service period, which generally corresponds to the vesting period, and is recognized as an increase to additional paid-in-capital in stockholders’ equity, and stock-based compensation expense is reflected in other operating expenses in the consolidated statements of income.
Earnings Per Share	Earnings Per Share Basic earnings per share exclude any dilutive effects of any outstanding options. Diluted earnings per share include the dilutive effects assuming outstanding stock options were exercised.
Future Adoption of New Accounting Standards	New Accounting Pronouncements Changes to the general accounting principles are established by the Financial Accounting Standards Board (“FASB”) in the form of accounting standards updates to the FASB Accounting Standards Codification TM . Accounting standards updates not listed below were assessed and determined to be either not applicable or are expected to have minimal impact on the Company’s consolidated financial statements. Adoption of New Accounting Standards Stock Compensation In March 2016, the FASB updated the general accounting principal for Stock Compensation which changed how companies account for certain aspects of share-based payment awards to employees. The updated guidance requires excess tax benefits and deficiencies from share-based payment awards be recorded in income tax expense in the income statement. Previously, excess tax benefits and deficiencies were recognized in shareholders’ equity or deferred taxes on the balance sheet depending on the tax situation of the Company. In addition, the updated guidance also changes the accounting for forfeitures and statutory tax withholding requirements, as well as the classification in the statement of cash flows. The new standard generally requires a modified retrospective transition through a cumulative-effect adjustment as of the beginning of the period of adoption, with certain provisions requiring either a prospective or retrospective transition. The Company adopted the new guidance on January 1, 2017. Upon adoption, the Company recognized excess tax benefits of approximately $17.7 million in deferred tax assets that were previously not recognized in a cumulative-effect adjustment increasing retained earnings by $17.7 million . The Company also recorded excess tax benefits of approximately $10.5 million in the provision for income taxes for the year ended December 31, 2017. The number of weighted average diluted shares outstanding were also adjusted to exclude excess tax benefits from the assumed proceeds in the diluted shares calculation resulting in an immaterial increase in the number of dilutive shares outstanding. The Company also elected to continue estimating forfeitures for purposes of recognizing share-based compensation. Other aspects of the adoption of the updated guidance did not have a material impact to the Company’s financial statements. Reporting Comprehensive Income In February 2018, the FASB updated the general accounting principle for Reporting Comprehensive Income to require reclassification from accumulated other comprehensive income to retained earnings for the stranded tax effects resulting from the newly enacted U.S. federal corporate income tax rate. The amount of the reclassification would be the difference between the historical U.S. federal corporate income tax rate and the newly enacted 21 percent tax rate. The Company adopted the new guidance on December 31, 2017 by reclassifying certain income tax effects of items within accumulated other comprehensive income to retained earnings as a result of the Tax Cuts and Jobs Act of 2017. The impact of adopting this standard was an increase in accumulated other comprehensive income and a reduction in retained earnings of approximately $156.4 million . Future Adoption of New Accounting Standards Financial Instruments In January 2016, the FASB amended the general accounting principle for Financial Instruments, which requires equity investments that are not accounted for under the equity method of accounting to be measured at fair value with changes recognized in net income and also updates certain presentation and disclosure requirements. The new guidance became effective for the Company beginning January 1, 2018 and required a cumulative-effect adjustment for certain items upon adoption. The adoption of the new guidance was not material to the Company’s consolidated financial statements. In June 2016, the FASB amended the existing impairment guidance of Financial Instruments. The amendment adds to U.S. GAAP an impairment model, known as current expected credit loss (“CECL”) model that is based on expected losses rather than incurred losses. For traditional and other receivables, held-to-maturity debt securities, loans and other instruments entities will be required to use the new forward-looking “expected loss” model that generally will result in earlier recognition of allowance for losses. For available-for-sale debt securities with unrealized losses, entities will measure credit losses similar to what they do today, except the losses will be recognized as allowances rather than reduction to the amortized cost of the securities. This guidance is effective for the Company January 1, 2020, with early adoption permitted. The guidance will be adopted through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective (that is, a modified-retrospective approach). The Company is currently evaluating the impact of this amendment on its consolidated financial statements. Leases In February 2016, the FASB issued guidance which will replace most existing lease accounting guidance. The new standard, based on the principle that entities should recognize assets and liabilities arising from leases, does not significantly change the lessees’ recognition, measurement and presentation of expenses and cash flows from the previous accounting standard. Leases are classified as finance or operating. The new standard’s primary change is the requirement for entities to recognize a lease liability for payments and a right of use asset representing the right to use the leased asset during the term of operating lease arrangements. Lessees are permitted to make an accounting policy election to not recognize the asset and liability for leases with a term of twelve months or less. Lessors’ accounting is largely unchanged from the previous accounting standard. In addition, the new standard expands the disclosure requirements of lease arrangements. Lessees and lessors will use a modified retrospective transition approach, which includes a number of practical expedients. This guidance is effective for the Company January 1, 2019, with early adoption permitted. The Company is currently evaluating the impact of this amendment on its consolidated financial statements; however, it does not expect the adoption of the new standard to have a material impact on its results of operations or balance sheet as a result of the recognition of right-to-use assets and lease liabilities related to operating leases. Contractual obligations related to operating leases totaled approximately $38.2 million as of December 31, 2017. Income Taxes In October 2016, the FASB amended the general accounting principal for Income Taxes, effective for the Company January 1, 2018. The amendment requires entities to recognize the tax consequences of intercompany asset transfers, except for inventory, at the transaction date. Current GAAP prohibits entities from recognizing the income tax consequences from intercompany asset transfers. The seller defers any net tax effect, and the buyer is prohibited from recognizing a deferred tax asset on the difference between the newly created tax basis of the asset in its tax jurisdiction and its financial statement carrying amount as reported in the consolidated financial statements. The amendment requires entities to recognize these tax consequences in the period in which the transfer occurred. There will be an immediate effect on earnings if the tax rates in the seller’s and buyer’s tax jurisdictions are different. This amendment will be applied using a modified retrospective transition method with a cumulative effect adjustment to retained earnings as of the beginning of the period of adoption. The adoption of this amendment is not expected to have a material impact on the Company’s consolidated financial statements. Derivative and Hedging In August 2017, the FASB updated the general accounting principal for Derivatives and Hedging. The updated guidance improves the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements and make certain targeted improvements to simplify the application of the hedge accounting in current GAAP related to the assessment of hedge effectiveness. The updated guidance is effective for the Company January 1, 2019, with early adoption permitted. The Company is currently evaluating the impact of this updated guidance on its consolidated financial statements.

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Investments [Abstract]
Available-for-sale Securities [Table Text Block]	The following tables provide information relating to investments in fixed maturity and equity securities by sector as of December 31, 2017 and 2016 (dollars in thousands): December 31, 2017: Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value % of Total Other-than- temporary impairments in AOCI Available-for-sale: Corporate $ 21,966,803 $ 1,299,594 $ 55,429 $ 23,210,968 60.9 % $ — Canadian government 2,843,273 1,378,510 1,707 4,220,076 11.1 — RMBS 1,695,126 36,632 11,878 1,719,880 4.5 — ABS 1,634,758 18,798 5,194 1,648,362 4.3 275 CMBS 1,285,594 22,627 4,834 1,303,387 3.4 — U.S. government 1,953,436 12,089 21,933 1,943,592 5.1 — State and political subdivisions 647,727 59,997 4,296 703,428 1.8 — Other foreign government 3,254,695 154,507 8,075 3,401,127 8.9 — Total fixed maturity securities $ 35,281,412 $ 2,982,754 $ 113,346 $ 38,150,820 100.0 % $ 275 Non-redeemable preferred stock $ 41,553 $ 479 $ 2,226 $ 39,806 39.7 % Other equity securities 61,288 479 1,421 60,346 60.3 Total equity securities $ 102,841 $ 958 $ 3,647 $ 100,152 100.0 % December 31, 2016: Amortized Unrealized Unrealized Estimated % of Total Other-than- Available-for-sale: Corporate $ 18,924,711 $ 911,618 $ 217,245 $ 19,619,084 61.1 % $ — Canadian government 2,561,605 1,085,982 3,541 3,644,046 11.4 — RMBS 1,258,039 33,917 13,380 1,278,576 4.0 (375 ) ABS 1,443,822 9,350 23,828 1,429,344 4.5 275 CMBS 1,342,440 28,973 7,759 1,363,654 4.2 — U.S. government 1,518,702 12,644 63,044 1,468,302 4.6 — State and political subdivisions 566,761 37,499 12,464 591,796 1.8 — Other foreign government 2,595,707 123,054 19,938 2,698,823 8.4 — Total fixed maturity securities $ 30,211,787 $ 2,243,037 $ 361,199 $ 32,093,625 100.0 % $ (100 ) Non-redeemable preferred stock $ 55,812 $ 1,648 $ 6,337 $ 51,123 18.6 % Other equity securities 229,767 1,792 7,321 224,238 81.4 Total equity securities $ 285,579 $ 3,440 $ 13,658 $ 275,361 100.0 %
Schedule of Financial Instruments Owned and Pledged as Collateral [Table Text Block]	The following table includes fixed maturity securities pledged and received as collateral and assets in trust held to satisfy collateral requirements under derivative transactions and certain third-party reinsurance treaties as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Fixed maturity securities pledged as collateral $ 72,542 $ 75,622 $ 207,066 $ 210,676 Fixed maturity securities received as collateral n/a 590,417 n/a 300,925 Assets in trust held to satisfy collateral requirements 15,584,296 16,715,281 12,135,258 12,874,370
Concentration Risk Disclosure [Text Block]	The Company’s exposure to concentrations of credit risk from single issuers greater than 10% of the Company’s stockholders’ equity included securities of the U.S. government and its agencies, as well as the securities disclosed below, as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Fixed maturity securities guaranteed or issued by: Canadian province of Quebec $ 1,119,337 $ 1,917,996 $ 1,004,261 $ 1,612,957 Canadian province of Ontario 939,837 1,282,944 832,764 1,126,433
Investments Classified By Contractual Maturity Date [Table Text Block]	Asset and mortgage-backed securities are shown separately in the table below, as they are not due at a single maturity date. Amortized Cost Estimated Fair Value Available-for-sale: Due in one year or less $ 864,993 $ 868,802 Due after one year through five years 7,988,167 8,234,097 Due after five years through ten years 9,286,543 9,781,323 Due after ten years 12,526,231 14,594,969 Asset and mortgage-backed securities 4,615,478 4,671,629 Total $ 35,281,412 $ 38,150,820
Fixed Maturity Holdings Industry Types [Table Text Block]	The tables below show the major industry types of the Company’s corporate fixed maturity holdings as of December 31, 2017 and 2016 (dollars in thousands): December 31, 2017: Amortized Cost Estimated Fair Value % of Total Finance $ 7,977,885 $ 8,362,774 36.1 % Industrial 11,535,166 12,199,333 52.5 Utility 2,453,752 2,648,861 11.4 Total $ 21,966,803 $ 23,210,968 100.0 % December 31, 2016: Amortized Cost Estimated Fair Value % of Total Finance $ 6,725,199 $ 6,888,968 35.2 % Industrial 10,228,813 10,639,613 54.2 Utility 1,970,699 2,090,503 10.6 Total $ 18,924,711 $ 19,619,084 100.0 %
Roll Forward Of Cumulative Credit Loss Component Of Otti Income Loss [Table Text Block]	The following table sets forth the amount of pre-tax credit loss impairments on fixed maturity securities held by the Company as of the dates indicated, for which a portion of the OTTI loss was recognized in AOCI, and the corresponding changes in such amounts (dollars in thousands): 2017 2016 2015 Balance, beginning of period $ 6,013 $ 7,284 $ 7,284 Additional impairments - credit loss OTTI recognized on securities previously impaired — 231 — Credit loss impairments previously recognized on securities impaired to fair value during the period (2,336 ) — — Credit loss previously recognized on securities which matured, paid down, prepaid or were sold during the period — (1,502 ) — Balance, end of period $ 3,677 $ 6,013 $ 7,284
Investments In Debt And Equity Securities Gross Unrealized Losses Disclosures [Table Text Block]	The following table presents the total gross unrealized losses for the 1,116 and 1,535 fixed maturity and equity securities at December 31, 2017 and 2016 , respectively, where the estimated fair value had declined and remained below amortized cost by the indicated amount (dollars in thousands): 2017 2016 Gross Unrealized Losses % of Total Gross Unrealized Losses % of Total Less than 20% $ 113,466 97.0 % $ 337,831 90.1 % 20% or more for less than six months 689 0.6 19,438 5.2 20% or more for six months or greater 2,838 2.4 17,588 4.7 Total $ 116,993 100.0 % $ 374,857 100.0 %
Fair Value And Investments In Debt And Equity Securities Disclosures [Table Text Block]	These investments are presented by class and grade of security, as well as the length of time the related fair value has remained below amortized cost (dollars in thousands): Less than 12 months 12 months or greater Total December 31, 2017: Estimated Fair Value Gross Unrealized Losses Estimated Gross Estimated Gross Investment grade securities: Corporate $ 1,886,212 $ 17,099 $ 1,009,750 $ 28,080 $ 2,895,962 $ 45,179 Canadian government 18,688 91 111,560 1,596 130,248 1,687 RMBS 566,699 5,852 224,439 6,004 791,138 11,856 ABS 434,274 2,707 168,524 2,434 602,798 5,141 CMBS 220,401 1,914 103,269 2,920 323,670 4,834 U.S. government 800,298 6,177 767,197 15,756 1,567,495 21,933 State and political subdivisions 43,510 242 68,666 4,054 112,176 4,296 Other foreign government 369,717 2,707 191,265 4,704 560,982 7,411 Total investment grade securities 4,339,799 36,789 2,644,670 65,548 6,984,469 102,337 Below investment grade securities: Corporate 194,879 3,317 75,731 6,933 270,610 10,250 Canadian government 1,995 20 — — 1,995 20 RMBS — — 1,369 22 1,369 22 ABS — — 1,489 53 1,489 53 Other foreign government 28,600 113 15,134 551 43,734 664 Total below investment grade securities 225,474 3,450 93,723 7,559 319,197 11,009 Total fixed maturity securities $ 4,565,273 $ 40,239 $ 2,738,393 $ 73,107 $ 7,303,666 $ 113,346 Non-redeemable preferred stock $ 82 $ 1 $ 26,471 $ 2,225 $ 26,553 $ 2,226 Other equity securities 5,820 1,023 47,251 398 53,071 1,421 Total equity securities $ 5,902 $ 1,024 $ 73,722 $ 2,623 $ 79,624 $ 3,647 Less than 12 months 12 months or greater Total December 31, 2016: Estimated Gross Estimated Gross Estimated Gross Investment grade securities: Corporate $ 4,661,706 $ 124,444 $ 549,273 $ 43,282 $ 5,210,979 $ 167,726 Canadian government 101,578 3,541 — — 101,578 3,541 RMBS 490,473 9,733 112,216 3,635 602,689 13,368 ABS 563,259 12,010 257,166 9,653 820,425 21,663 CMBS 368,465 6,858 10,853 166 379,318 7,024 U.S. government 1,056,101 63,044 — — 1,056,101 63,044 State and political subdivisions 187,194 9,396 13,635 3,068 200,829 12,464 Other foreign government 524,236 13,372 51,097 2,981 575,333 16,353 Total investment grade securities 7,953,012 242,398 994,240 62,785 8,947,252 305,183 Below investment grade securities: Corporate 330,757 7,914 163,152 41,605 493,909 49,519 RMBS — — 412 12 412 12 ABS 5,904 700 12,581 1,465 18,485 2,165 CMBS 5,815 735 — — 5,815 735 Other foreign government 32,355 1,258 39,763 2,327 72,118 3,585 Total below investment grade securities 374,831 10,607 215,908 45,409 590,739 56,016 Total fixed maturity securities $ 8,327,843 $ 253,005 $ 1,210,148 $ 108,194 $ 9,537,991 $ 361,199 Non-redeemable preferred stock $ 10,831 $ 831 $ 21,879 $ 5,506 $ 32,710 $ 6,337 Other equity securities 202,068 7,020 6,751 301 208,819 7,321 Total equity securities $ 212,899 $ 7,851 $ 28,630 $ 5,807 $ 241,529 $ 13,658
Investment Income [Table Text Block]	Major categories of investment income, net of related expenses consist of the following (dollars in thousands): 2017 2016 2015 Fixed maturity securities $ 1,401,585 $ 1,285,406 $ 1,177,706 Mortgage loans on real estate 197,755 168,582 149,564 Policy loans 60,617 63,837 62,955 Funds withheld at interest 457,774 368,728 343,031 Short-term investments and cash and cash equivalents 7,171 8,051 7,574 Other 110,460 89,371 61,709 Investment income 2,235,362 1,983,975 1,802,539 Investment expense (80,711 ) (72,089 ) (68,044 ) Investment income, net of related expenses $ 2,154,651 $ 1,911,886 $ 1,734,495
Gain (Loss) on Investments [Table Text Block]	Investment related gains (losses), net, consist of the following (dollars in thousands): 2017 2016 2015 Fixed maturity and equity securities: Other-than-temporary impairment losses on fixed maturities $ (42,639 ) $ (38,805 ) $ (57,380 ) Portion of loss recognized in accumulated other comprehensive income — 74 — Net other-than-temporary impairment losses on fixed maturity securities recognized in earnings $ (42,639 ) $ (38,731 ) $ (57,380 ) Impairment losses on equity securities (1,202 ) — — Gain on investment activity 110,569 154,370 73,079 Loss on investment activity (41,679 ) (49,965 ) (71,893 ) Other impairment losses and change in mortgage loan provision (9,497 ) (11,006 ) (6,953 ) Derivatives and other, net 152,328 39,527 (101,603 ) Total investment related gains (losses), net $ 167,880 $ 94,195 $ (164,750 )
Schedule of Repurchase Agreements [Table Text Block]	The following table includes the amount of borrowed securities, securities lent and securities collateral received as part of the securities lending program, repurchased/reverse repurchased securities pledged and received and cash received as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Borrowed securities $ 358,875 $ 377,820 $ 263,820 $ 279,186 Securities lending: Securities loaned 117,246 121,551 74,389 73,625 Securities received n/a 128,000 n/a 80,000 Repurchase program/reverse repurchase program: Securities pledged 413,819 428,344 476,531 499,891 Securities received n/a 417,550 n/a 515,200
Schedule of Underlying Assets of Repurchase Agreements when Amount of Repurchase Agreements Exceeds 10 Percent of Assets [Table Text Block]	The following tables present information on the Company’s securities lending and repurchase transactions as of December 31, 2017 and 2016 , respectively (dollars in thousands). Collateral associated with certain borrowed securities is not included within the tables as the collateral pledged to each counterparty is the right to reinsurance treaty cash flows. December 31, 2017 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total Securities lending transaction: Corporate $ — $ — $ — $ 121,551 $ 121,551 Total — — — 121,551 121,551 Repurchase transactions: Corporate — — 312 184,334 184,646 RMBS — — — — — U.S. government — — — 220,765 220,765 Foreign government — — — 21,802 21,802 Other 1,131 — — — 1,131 Total 1,131 — 312 426,901 428,344 Total transactions $ 1,131 $ — $ 312 $ 548,452 $ 549,895 Gross amount of recognized liabilities for securities lending and repurchase transactions in preceding table $ 576,786 Amounts related to agreements not included in offsetting disclosure $ 26,891 December 31, 2016 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total Securities lending transaction: Corporate $ — $ — $ 4,017 $ 69,608 $ 73,625 Total — — 4,017 69,608 73,625 Repurchase transactions: Corporate $ — $ — $ 3,220 $ 166,979 $ 170,199 RMBS — — — 92,546 92,546 U.S. government — — — 216,000 216,000 Foreign government — — — 19,900 19,900 Other 1,246 — — — 1,246 Total 1,246 — 3,220 495,425 499,891 Total transactions $ 1,246 $ — $ 7,237 $ 565,033 $ 573,516 Gross amount of recognized liabilities for repurchase transactions in preceding table $ 624,032 Amounts related to agreements not included in offsetting disclosure $ 50,516
Disclosure Of Real Estate Holdings By Property Type [Table Text Block]	The recorded investment in mortgage loans on real estate presented below is gross of unamortized deferred loan origination fees and expenses, and valuation allowances. The distribution of mortgage loans by property type is as follows as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Carrying Value Percentage of Total Carrying Value Percentage of Total Property type: Office building $ 1,487,392 33.6 % $ 1,270,113 33.6 % Retail 1,270,676 28.8 1,179,936 31.2 Industrial 938,612 21.3 713,461 18.8 Apartment 510,052 11.6 447,088 11.8 Other commercial 206,439 4.7 172,609 4.6 Recorded investment 4,413,171 100.0 % $ 3,783,207 100.0 % Unamortized balance of loan origination fees and expenses (3,254 ) — Valuation allowances (9,384 ) (7,685 ) Total mortgage loans on real estate $ 4,400,533 $ 3,775,522
Disclosure of Real Estate Holdings Classified By Contractual Maturity Date [Table Text Block]	The maturities of the mortgage loans as of December 31, 2017 and 2016 are as follows (dollars in thousands): 2017 2016 Recorded Investment % of Total Recorded Investment % of Total Due within five years $ 1,091,066 24.8 % $ 822,073 21.7 % Due after five years through ten years 2,516,872 57.0 2,099,559 55.5 Due after ten years 805,233 18.2 861,575 22.8 Total $ 4,413,171 100.0 % $ 3,783,207 100.0 %
Financing Receivable Credit Quality Indicators [Table Text Block]	The following tables set forth certain key credit quality indicators of the Company’s recorded investment in mortgage loans as of December 31, 2017 and 2016 (dollars in thousands): Recorded Investment Debt Service Ratios Construction loans >1.20x 1.00x - 1.20x <1.00x Total % of Total December 31, 2017: Loan-to-Value Ratio 0% - 59.99% $ 2,148,428 $ 53,979 $ 3,801 $ — $ 2,206,208 50.0 % 60% - 69.99% 1,517,029 47,128 43,921 — 1,608,078 36.4 70% - 79.99% 396,446 19,461 15,367 — 431,274 9.8 Greater than 80% 120,850 30,713 6,362 9,686 167,611 3.8 Total $ 4,182,753 $ 151,281 $ 69,451 $ 9,686 $ 4,413,171 100.0 % Recorded Investment Debt Service Ratios >1.20x 1.00x - 1.20x <1.00x Total % of Total December 31, 2016: Loan-to-Value Ratio 0% - 59.99% $ 1,859,640 $ 64,749 $ 1,366 $ 1,925,755 50.8 % 60% - 69.99% 1,257,788 34,678 — 1,292,466 34.2 70% - 79.99% 370,092 20,869 24,369 415,330 11.0 Greater than 80% 114,297 — 35,359 149,656 4.0 Total $ 3,601,817 $ 120,296 $ 61,094 $ 3,783,207 100.0 %
Past Due Financing Receivables [Table Text Block]	The age analysis of the Company’s past due recorded investments in mortgage loans as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 31-60 days past due $ 17,100 $ — 61-90 days past due 2,056 — Total past due 19,156 — Current 4,394,015 3,783,207 Total $ 4,413,171 $ 3,783,207
Recorded Investment And Allowance For Credit Losses [Table Text Block]	The following table presents the recorded investment in mortgage loans, by method of measuring impairment, and the related valuation allowances, as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Mortgage loans: Individually measured for impairment $ 5,858 $ 2,216 Collectively measured for impairment 4,407,313 3,780,991 Recorded investment 4,413,171 3,783,207 Valuation allowances: Individually measured for impairment — — Collectively measured for impairment 9,384 7,685 Total valuation allowances 9,384 7,685
Allowance For Loan And Lease Losses Provision For Loss Net [Table Text Block]	Information regarding the Company’s loan valuation allowances for mortgage loans as of December 31, 2017, 2016 and 2015 are as follows (dollars in thousands): 2017 2016 2015 Balance, beginning of period $ 7,685 $ 6,813 $ 6,471 Provision 1,691 872 342 Translation adjustment 8 — — Balance, end of period $ 9,384 $ 7,685 $ 6,813
Impaired Financing Receivables [Table Text Block]	Information regarding the portion of the Company’s mortgage loans that were impaired as of December 31, 2017 and 2016 is as follows (dollars in thousands): Unpaid Principal Balance Recorded Investment Related Allowance Carrying Value December 31, 2017: Impaired mortgage loans with no valuation allowance recorded $ 6,427 $ 5,858 $ — $ 5,858 Impaired mortgage loans with valuation allowance recorded — — — — Total impaired mortgage loans $ 6,427 $ 5,858 $ — $ 5,858 December 31, 2016: Impaired mortgage loans with no valuation allowance recorded $ 2,758 $ 2,216 $ — $ 2,216 Impaired mortgage loans with valuation allowance recorded — — — — Total impaired mortgage loans $ 2,758 $ 2,216 $ — $ 2,216 The Company’s average investment balance of impaired mortgage loans and the related interest income are reflected in the table below for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): 2017 2016 2015 Average Investment (1) Interest Income Average Investment (1) Interest Income Average Investment (1) Interest Income Impaired mortgage loans with no valuation allowance recorded $ 3,621 $ 186 $ 2,249 $ 142 $ 6,033 $ 330 Impaired mortgage loans with valuation allowance recorded — — — — 11,592 770 Total $ 3,621 $ 186 $ 2,249 $ 142 $ 17,625 $ 1,100 (1) Average recorded investment represents the average loan balances as of the beginning of period and all subsequent quarterly end of period balances.
Schedule of Other Assets [Table Text Block]	Other invested assets represented approximately 3.1% and 3.6% of the Company’s total investments as of December 31, 2017 and 2016 , respectively. Carrying values of these assets as of December 31, 2017 and 2016 are as follows (dollars in thousands): 2017 2016 Equity securities $ 100,152 $ 275,361 Limited partnerships and real estate joint ventures 781,124 687,522 Derivatives 137,613 229,108 FVO contractholder-directed unit-linked investments 218,541 190,120 Other 368,054 209,829 Total other invested assets $ 1,605,484 $ 1,591,940

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]	The following table presents the notional amounts and gross fair value of derivative instruments prior to taking into account the netting effects of master netting agreements as of December 31, 2017 and 2016 (dollars in thousands): December 31, 2017 December 31, 2016 Notional Carrying Value/Fair Value Notional Carrying Value/Fair Value Amount Assets Liabilities Amount Assets Liabilities Derivatives not designated as hedging instruments: Interest rate swaps $ 996,204 $ 59,809 $ 2,372 $ 949,556 $ 78,405 $ 5,949 Financial futures 412,438 — — 475,968 — — Foreign currency forwards 6,030 — 28 25,000 — 5,070 Consumer price index swaps 221,932 — 2,160 20,615 — 262 Credit default swaps 961,200 8,319 1,651 926,000 12,012 2,871 Equity options 632,251 23,271 — 525,894 33,459 — Longevity swaps 960,400 40,659 — 841,360 26,958 — Mortality swaps — — 1,683 50,000 — 2,462 Synthetic guaranteed investment contracts 10,052,576 — — 8,834,700 — — Embedded derivatives in: Modified coinsurance or funds withheld arrangements — 122,194 — — — 22,529 Indexed annuity products — — 861,758 — — 805,672 Variable annuity products — — 152,470 — — 184,636 Total non-hedging derivatives 14,243,031 254,252 1,022,122 12,649,093 150,834 1,029,451 Derivatives designated as hedging instruments: Interest rate swaps 435,000 — 20,389 435,000 27,901 31,223 Foreign currency swaps 672,921 65,207 8,496 928,505 104,359 734 Foreign currency forwards 553,175 1,265 7,720 — — — Total hedging derivatives 1,661,096 66,472 36,605 1,363,505 132,260 31,957 Total derivatives $ 15,904,127 $ 320,724 $ 1,058,727 $ 14,012,598 $ 283,094 $ 1,061,408
Offsetting Assets [Table Text Block]	Gross Amounts Not Offset in the Balance Sheet Gross Amounts Recognized Gross Amounts Offset in the Balance Sheet Net Amounts Presented in the Balance Sheet Financial Instruments (1) Cash Collateral Pledged/ Received Net Amount December 31, 2017: Derivative assets $ 198,530 $ (20,258 ) $ 178,272 $ (862 ) $ (185,900 ) $ (8,490 ) Derivative liabilities 44,499 (20,258 ) 24,241 (58,156 ) (22,221 ) (56,136 ) December 31, 2016: Derivative assets $ 283,094 $ (27,028 ) $ 256,066 $ (16,913 ) $ (254,498 ) $ (15,345 ) Derivative liabilities 48,571 (27,028 ) 21,543 (95,863 ) (1,441 ) (75,761 )
Offsetting Liabilities [Table Text Block]	Gross Amounts Not Offset in the Balance Sheet Gross Amounts Recognized Gross Amounts Offset in the Balance Sheet Net Amounts Presented in the Balance Sheet Financial Instruments (1) Cash Collateral Pledged/ Received Net Amount December 31, 2017: Derivative assets $ 198,530 $ (20,258 ) $ 178,272 $ (862 ) $ (185,900 ) $ (8,490 ) Derivative liabilities 44,499 (20,258 ) 24,241 (58,156 ) (22,221 ) (56,136 ) December 31, 2016: Derivative assets $ 283,094 $ (27,028 ) $ 256,066 $ (16,913 ) $ (254,498 ) $ (15,345 ) Derivative liabilities 48,571 (27,028 ) 21,543 (95,863 ) (1,441 ) (75,761 )
Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block]	The gain or loss on the hedged item attributable to a change in foreign currency and the offsetting gain or loss on the related foreign currency swaps as of December 31, 2017, 2016 and 2015 were (dollars in thousands): Type of Fair Value Hedge Hedged Item Gains (Losses) Recognized for Derivatives Gains (Losses) Recognized for Hedged Items Ineffectiveness Recognized in Investment Related Gains (Losses) For the Year Ended December 31, 2017: Foreign currency swaps Foreign-denominated fixed maturity securities $ 9,456 $ (9,456 ) $ — For the Year Ended December 31, 2016: Foreign currency swaps Foreign-denominated fixed maturity securities $ (1,700 ) $ 1,700 $ — For the Year Ended December 31, 2015: Foreign currency swaps Foreign-denominated fixed maturity securities $ 4,008 $ (4,008 ) $ —
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following table presents the components of AOCI, before income tax, and the consolidated income statement classification where the gain or loss is recognized related to cash flow hedges for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): Amounts Included in AOCI Balance December 31, 2014 $ (31,591 ) Gains (losses) deferred in other comprehensive income (loss) on the effective portion of cash flow hedges 2,676 Amounts reclassified to investment related (gains) losses, net 87 Amounts reclassified to investment income (569 ) Balance December 31, 2015 (29,397 ) Gains (losses) deferred in other comprehensive income (loss) on the effective portion of cash flow hedges 27,110 Amounts reclassified to investment related (gains) losses, net 278 Amounts reclassified to investment income (487 ) Balance December 31, 2016 (2,496 ) Gains (losses) deferred in other comprehensive income (loss) on the effective portion of cash flow hedges 6,316 Amounts reclassified to investment related (gains) losses, net (775 ) Amounts reclassified to investment income (505 ) Amounts reclassified to interest expense 79 Balance December 31, 2017 $ 2,619
Schedule of Cash Flow Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block]	The following table presents the effective portion of derivatives in cash flow hedging relationships on the consolidated statements of income and the consolidated statements of stockholders’ equity for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): Effective Portion Derivative Type Gains (Losses) Deferred in OCI Gains (Losses) Reclassified into Income from OCI For the year ended December 31, 2017: Investment Related Gains (Losses) Investment Income Interest Expense Interest rate $ (5,649 ) $ — $ — $ (79 ) Currency/Interest rate 11,955 — 380 — Forward bond purchase commitments 10 775 125 — Total $ 6,316 $ 775 $ 505 $ (79 ) For the year ended December 31, 2016: Interest rate $ 27,901 $ — $ — $ — Currency/Interest rate (791 ) — 510 — Forward bond purchase commitments — (278 ) (23 ) — Total $ 27,110 $ (278 ) $ 487 $ — For the year ended December 31, 2015: Currency/Interest rate $ (11,422 ) $ — $ 343 $ — Forward bond purchase commitments 14,098 (87 ) 226 — Total $ 2,676 $ (87 ) $ 569 $ — The following table presents the effective portion of derivatives in cash flow hedging relationships on the consolidated statements of income and the consolidated statements of stockholders’ equity for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands):
Schedule of Net Investment Hedges, Statements of Financial Performance and Financial Position, Location [Table Text Block]	The following table illustrates the Company’s net investments in foreign operations (“NIFO”) hedges for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): Derivative Gains (Losses) Deferred in AOCI For the year ended Type of NIFO Hedge (1) (2) 2017 2016 2015 Foreign currency swaps $ (37,567 ) $ (10,234 ) $ 96,019 Foreign currency forwards (10,386 ) — — (1) There were no sales or substantial liquidations of net investments in foreign operations that would have required the reclassification of gains or losses from accumulated other comprehensive income (loss) into investment income during the periods presented. (2) There was no ineffectiveness recognized for the Company’s hedges of net investments in foreign operations.
Derivative Instruments Gain Loss By Income Statement Location [Table Text Block]	A summary of the effect of non-hedging derivatives, including embedded derivatives, on the Company’s consolidated statements of income for the years ended December 31, 2017, 2016 and 2015 is as follows (dollars in thousands): Gains (Losses) for the Years Ended December 31, Type of Non-hedging Derivative Income Statement Location of Gains (Losses) 2017 2016 2015 Interest rate swaps Investment related gains (losses), net $ 11,278 $ 7,649 $ 20,358 Interest rate options Investment related gains (losses), net — — 3,275 Financial futures Investment related gains (losses), net (36,160 ) (40,242 ) 319 Foreign currency forwards Investment related gains (losses), net 591 1,630 (1,160 ) Consumer price index swaps Investment related gains (losses), net (2,078 ) (401 ) (208 ) Credit default swaps Investment related gains (losses), net 18,118 18,100 (4,683 ) Equity options Investment related gains (losses), net (42,953 ) (28,270 ) (16,899 ) Longevity swaps Other revenues 9,358 13,095 8,228 Mortality swaps Other revenues (921 ) (172 ) (1,822 ) Subtotal (42,767 ) (28,611 ) 7,408 Embedded derivatives in: Modified coinsurance or funds withheld arrangements Investment related gains (losses), net 144,723 54,169 (98,792 ) Indexed annuity products Interest credited (80,062 ) 10,708 19,440 Variable annuity products Investment related gains (losses), net 32,166 7,835 (33,192 ) Total non-hedging derivatives $ 54,060 $ 44,101 $ (105,136 )
Disclosure Of Credit Derivatives [Table Text Block]	The following table presents the estimated fair value, maximum amount of future payments and weighted average years to maturity of credit default swaps sold by the Company at December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Rating Agency Designation of Referenced Credit Obligations (1) Estimated Fair Value of Credit Default Swaps Maximum Amount of Future Payments under Credit Default Swaps (2) Weighted Average Years to Maturity (3) Estimated Fair Maximum (2) Weighted (3) AAA/AA+/AA/AA-/A+/A/A- Single name credit default swaps $ 3,128 $ 162,000 2.9 $ 1,726 $ 150,500 3.8 Subtotal 3,128 162,000 2.9 1,726 150,500 3.8 BBB+/BBB/BBB- Single name credit default swaps 4,469 361,700 2.9 1,426 347,200 3.7 Credit default swaps referencing indices (55 ) 422,600 4.0 6,295 416,000 5.0 Subtotal 4,414 784,300 3.5 7,721 763,200 4.4 BB+/BB/BB- Single name credit default swaps 30 5,000 1.5 (477 ) 9,000 3.5 Subtotal 30 5,000 1.5 (477 ) 9,000 3.5 Total $ 7,572 $ 951,300 3.4 $ 8,970 $ 922,700 4.3 (1) The rating agency designations are based on ratings from Standard and Poor’s (“S&P”). (2) Assumes the value of the referenced credit obligations is zero. (3) The weighted average years to maturity of the credit default swaps is calculated based on weighted average notional amounts.
Changes In Estimated Fair Value Related To Embedded Derivatives [Table Text Block]	The related gains (losses) and the effect on net income after amortization of DAC and income taxes for the years ended December 31, 2017, 2016 and 2015 are reflected in the following table (dollars in thousands): 2017 2016 2015 Embedded derivatives in modified coinsurance or funds withheld arrangements included in investment related gains $ 144,723 $ 54,169 $ 98,792 After the associated amortization of DAC and taxes, the related amounts included in net income 48,316 9,160 (26,025 ) Embedded derivatives in variable annuity contracts included in investment related gains 32,166 7,835 (33,192 ) After the associated amortization of DAC and taxes, the related amounts included in net income 53,645 (41,201 ) (29,008 ) Amounts related to embedded derivatives in equity-indexed annuities included in benefits and expenses (80,062 ) 10,708 19,440 After the associated amortization of DAC and taxes, the related amounts included in net income (68,808 ) (4,148 ) 6,204
Credit Risk [Table Text Block]	Information regarding the Company’s credit exposure related to its over-the-counter derivative contracts, centrally cleared derivative contracts and margin account for exchange-traded futures at December 31, 2017 and 2016 is reflected in the following table (dollars in thousands): 2017 2016 Estimated fair value of derivatives in net asset position $ 155,714 $ 236,985 Cash provided as collateral (1) 22,221 1,441 Securities pledged to counterparties as collateral (2) 58,156 95,863 Cash pledged from counterparties as collateral (3) (185,900 ) (254,498 ) Securities pledged from counterparties as collateral (4) (862 ) (16,913 ) Initial margin for cleared derivatives (58,156 ) (73,571 ) Net amount after application of master netting agreements and collateral $ (8,827 ) $ (10,693 ) Margin account related to exchange-traded futures (5) $ 6,538 $ 9,687 (1) Consists of receivable from counterparty, included in other assets. (2) Included in available-for-sale securities, primarily consists of U.S. Treasury and government agency securities. (3) Included in cash and cash equivalents, with obligation to return cash collateral recorded in other liabilities. (4) Consists of U.S. Treasury and government agency securities. (5) Included in other assets.

Fair Value of Assets and Liab37

Fair Value of Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	Assets and liabilities measured at fair value on a recurring basis as of December 31, 2017 and December 31, 2016 are summarized below (dollars in thousands): December 31, 2017: Fair Value Measurements Using: Total Level 1 Level 2 Level 3 Assets: Fixed maturity securities – available-for-sale: Corporate $ 23,210,968 $ — $ 21,873,696 $ 1,337,272 Canadian government 4,220,076 — 3,626,134 593,942 RMBS 1,719,880 — 1,611,998 107,882 ABS 1,648,362 — 1,524,888 123,474 CMBS 1,303,387 — 1,300,153 3,234 U.S. government 1,943,592 1,818,006 103,075 22,511 State and political subdivisions 703,428 — 662,225 41,203 Other foreign government 3,401,127 — 3,396,035 5,092 Total fixed maturity securities – available-for-sale 38,150,820 1,818,006 34,098,204 2,234,610 Funds withheld at interest – embedded derivatives 122,194 — — 122,194 Cash equivalents 356,788 354,071 2,717 — Short-term investments 50,746 — 47,650 3,096 Other invested assets: Non-redeemable preferred stock 39,806 39,806 — — Other equity securities 60,346 60,346 — — Derivatives: Interest rate swaps 51,359 — 51,359 — Foreign currency forwards 730 — 730 — CPI swaps (221 ) — (221 ) — Credit default swaps 5,908 — 5,908 — Equity options 16,932 — 16,932 — Foreign currency swaps 62,905 — 62,905 — FVO contractholder-directed unit-linked investments 218,541 217,618 923 — Total other invested assets 456,306 317,770 138,536 — Other assets - longevity swaps 40,659 — — 40,659 Total $ 39,177,513 $ 2,489,847 $ 34,287,107 $ 2,400,559 Liabilities: Interest sensitive contract liabilities – embedded derivatives $ 1,014,228 $ — $ — $ 1,014,228 Other liabilities: Derivatives: Interest rate swaps 14,311 — 14,311 — Foreign currency forwards 7,213 — 7,213 — CPI swaps 1,939 — 1,939 — Credit default swaps (760 ) — (760 ) — Equity options (6,339 ) — (6,339 ) — Foreign currency swaps 6,194 — 6,194 — Mortality swaps 1,683 — — 1,683 Total $ 1,038,469 $ — $ 22,558 $ 1,015,911 December 31, 2016: Fair Value Measurements Using: Total Level 1 Level 2 Level 3 Assets: Fixed maturity securities – available-for-sale: Corporate $ 19,619,084 $ 310,995 $ 18,035,836 $ 1,272,253 Canadian government 3,644,046 — 3,168,081 475,965 RMBS 1,278,576 — 1,118,285 160,291 ABS 1,429,344 — 1,210,064 219,280 CMBS 1,363,654 — 1,342,509 21,145 U.S. government 1,468,302 1,345,755 98,059 24,488 State and political subdivisions 591,796 — 550,130 41,666 Other foreign government 2,698,823 276,729 2,409,225 12,869 Total fixed maturity securities – available-for-sale 32,093,625 1,933,479 27,932,189 2,227,957 Funds withheld at interest – embedded derivatives (22,529 ) — — (22,529 ) Cash equivalents 338,601 338,601 — — Short-term investments 44,241 8,276 32,619 3,346 Other invested assets: Non-redeemable preferred stock 51,123 38,317 12,806 — Other equity securities 224,238 224,238 — — Derivatives: Interest rate swaps 93,508 — 93,508 — Credit default swaps 9,136 — 9,136 — Equity options 26,070 — 26,070 — Foreign currency swaps 100,394 — 100,394 — FVO contractholder-directed unit-linked investments 190,120 188,891 1,229 — Other 11,036 11,036 — — Total other invested assets 705,625 462,482 243,143 — Other assets - longevity swaps 26,958 — — 26,958 Total $ 33,186,521 $ 2,742,838 $ 28,207,951 $ 2,235,732 Liabilities: Interest sensitive contract liabilities – embedded derivatives $ 990,308 $ — $ — $ 990,308 Other liabilities: Derivatives: Interest rate swaps 24,374 — 24,374 — Foreign currency forwards 5,070 — 5,070 — CPI swaps 262 — 262 — Credit default swaps (5 ) — (5 ) — Equity options (7,389 ) — (7,389 ) — Foreign currency swaps (3,231 ) — (3,231 ) — Mortality swaps 2,462 — — 2,462 Total $ 1,011,851 $ — $ 19,081 $ 992,770
Fair Value Inputs, Assets, Quantitative Information [Table Text Block]	The following table presents quantitative information about significant unobservable inputs used in Level 3 fair value measurements that are developed internally by the Company as of December 31, 2017 and 2016 (dollars in thousands): Fair Value Valuation Unobservable Range (Weighted Average) Assets: 2017 2016 Technique Input 2017 2016 Corporate $ 173,579 $ 167,815 Market comparable securities Liquidity premium 0-2% (1%) 0-2% (1%) U.S. government 22,511 24,488 Market comparable securities Liquidity premium 0-1% (1%) 0-1% (1%) State and political subdivisions 4,616 4,670 Market comparable securities Liquidity premium 1 % 1 % Funds withheld at interest- embedded derivatives 122,194 (22,529 ) Total return swap Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (8%) Withdrawal 0-5% (3%) 0-5% (3%) CVA 0-5% (1%) 0-5% (1%) Crediting rate 2-4% (2%) 2-4% (2%) Longevity swaps 40,659 26,958 Discounted cash flow Mortality 0-100% (2%) 0-100% (2%) Mortality improvement (10%)-10% (3%) (10%)-10% (3%) Liabilities: Interest sensitive contract liabilities- embedded derivatives- indexed annuities 861,758 805,672 Discounted cash flow Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (8%) Withdrawal 0-5% (3%) 0-5% (3%) Option budget projection 2-4% (2%) 2-4% (2%) Interest sensitive contract liabilities- embedded derivatives- variable annuities 152,470 184,636 Discounted cash flow Mortality 0-100% (1%) 0-100% (2%) Lapse 0-25% (5%) 0-25% (6%) Withdrawal 0-7% (3%) 0-7% (3%) CVA 0-5% (1%) 0-5% (1%) Long-term volatility 0-27% (8%) 0-27% (14%) Mortality swaps 1,683 2,462 Discounted cash flow Mortality 0-100% (1%) 0-100% (1%)
Fair Value Inputs, Liabilities, Quantitative Information [Table Text Block]	The following table presents quantitative information about significant unobservable inputs used in Level 3 fair value measurements that are developed internally by the Company as of December 31, 2017 and 2016 (dollars in thousands): Fair Value Valuation Unobservable Range (Weighted Average) Assets: 2017 2016 Technique Input 2017 2016 Corporate $ 173,579 $ 167,815 Market comparable securities Liquidity premium 0-2% (1%) 0-2% (1%) U.S. government 22,511 24,488 Market comparable securities Liquidity premium 0-1% (1%) 0-1% (1%) State and political subdivisions 4,616 4,670 Market comparable securities Liquidity premium 1 % 1 % Funds withheld at interest- embedded derivatives 122,194 (22,529 ) Total return swap Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (8%) Withdrawal 0-5% (3%) 0-5% (3%) CVA 0-5% (1%) 0-5% (1%) Crediting rate 2-4% (2%) 2-4% (2%) Longevity swaps 40,659 26,958 Discounted cash flow Mortality 0-100% (2%) 0-100% (2%) Mortality improvement (10%)-10% (3%) (10%)-10% (3%) Liabilities: Interest sensitive contract liabilities- embedded derivatives- indexed annuities 861,758 805,672 Discounted cash flow Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (8%) Withdrawal 0-5% (3%) 0-5% (3%) Option budget projection 2-4% (2%) 2-4% (2%) Interest sensitive contract liabilities- embedded derivatives- variable annuities 152,470 184,636 Discounted cash flow Mortality 0-100% (1%) 0-100% (2%) Lapse 0-25% (5%) 0-25% (6%) Withdrawal 0-7% (3%) 0-7% (3%) CVA 0-5% (1%) 0-5% (1%) Long-term volatility 0-27% (8%) 0-27% (14%) Mortality swaps 1,683 2,462 Discounted cash flow Mortality 0-100% (1%) 0-100% (1%)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Level Transfers [Table Text Block]	December 31, 2017 (dollars in thousands): 2017 Transfers from Level 1 to Level 2 Transfers from Level 2 to Level 1 Fixed maturity securities - available-for-sale: Corporate $ 596,809 $ 88,674 Other foreign government 317,640 —
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	For the year ended December 31, 2017: Fixed maturity securities - available-for-sale Corporate Canadian government RMBS ABS Fair value, beginning of period $ 1,272,253 $ 475,965 $ 160,291 $ 219,280 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (1,429 ) 13,180 (346 ) 1,776 Investment related gains (losses), net 4,991 — 729 245 Included in other comprehensive income (6,719 ) 104,797 2,341 7,044 Purchases (1) 408,995 — 76,792 45,215 Sales (1) (89,248 ) — (28,043 ) — Settlements (1) (285,958 ) — (18,988 ) (87,328 ) Transfers into Level 3 47,360 — 9,100 85,152 Transfers out of Level 3 (12,973 ) — (93,994 ) (147,910 ) Fair value, end of period $ 1,337,272 $ 593,942 $ 107,882 $ 123,474 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ (1,457 ) $ 13,180 $ (196 ) $ 669 Investment related gains (losses), net (5,389 ) — (346 ) — For the year ended December 31, 2017 (continued): Fixed maturity securities - available-for-sale CMBS U.S. government State Other foreign government Short-term investments Fair value, beginning of period $ 21,145 $ 24,488 $ 41,666 $ 12,869 $ 3,346 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses 709 (461 ) (55 ) (1 ) — Investment related gains (losses), net (595 ) — — — — Included in other comprehensive income (71 ) 19 (15 ) (252 ) 11 Purchases (1) — 465 — 496 3,703 Sales (1) (3,720 ) — — — — Settlements (1) (5,404 ) (2,000 ) (843 ) (672 ) (335 ) Transfers into Level 3 1,302 — 7,294 — — Transfers out of Level 3 (10,132 ) — (6,844 ) (7,348 ) (3,629 ) Fair value, end of period $ 3,234 $ 22,511 $ 41,203 $ 5,092 $ 3,096 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ — $ (461 ) $ (54 ) $ (1 ) $ — For the year ended December 31, 2017 (continued): Funds withheld at interest-embedded derivatives Other assets - longevity swaps Interest Other liabilities - mortality swaps Fair value, beginning of period $ (22,529 ) $ 26,958 $ (990,308 ) $ (2,462 ) Total gains/losses (realized/unrealized) Included in earnings, net: Investment related gains (losses), net 144,723 — 32,166 — Interest credited — — (80,062 ) — Included in other comprehensive income — 4,343 — — Other revenue — 9,358 — (921 ) Purchases (1) — — (55,237 ) — Sales (1) — — — — Settlements (1) — — 79,213 1,700 Fair value, end of period $ 122,194 $ 40,659 $ (1,014,228 ) $ (1,683 ) Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment related gains (losses), net $ 144,723 $ — $ 23,472 $ — Other revenue — 9,358 — (921 ) Interest credited — — (159,276 ) — For the year ended December 31, 2016: Fixed maturity securities - available-for-sale Corporate Canadian government RMBS ABS Fair value, beginning of period $ 1,226,970 $ 416,076 $ 330,649 $ 303,836 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (2,399 ) 12,197 (595 ) 801 Investment related gains (losses), net (4,756 ) — (2,153 ) 1,101 Included in other comprehensive income 10,022 47,692 (1,621 ) (2,696 ) Purchases (1) 312,720 — 103,553 138,522 Sales (1) (60,399 ) — (167,684 ) (38,681 ) Settlements (1) (195,016 ) — (38,495 ) (61,770 ) Transfers into Level 3 14,098 — 1,728 56,105 Transfers out of Level 3 (28,987 ) — (65,091 ) (177,938 ) Fair value, end of period $ 1,272,253 $ 475,965 $ 160,291 $ 219,280 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ (2,343 ) $ 12,197 $ (158 ) $ 734 Investment related gains (losses), net (817 ) — (231 ) — For the year ended December 31, 2016 (continued): Fixed maturity securities - available-for-sale CMBS U.S. government State Other foreign government Short-term investments Fair value, beginning of period $ 68,563 $ 26,265 $ 38,342 $ 14,065 $ — Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses 1,677 (487 ) 215 — — Investment related gains (losses), net (876 ) — — — — Included in other comprehensive income (5,887 ) 39 962 110 — Purchases (1) 1,545 508 6,952 — 3,365 Sales (1) (41,143 ) — — — — Settlements (1) (552 ) (1,837 ) (599 ) (1,306 ) (19 ) Transfers into Level 3 — — — — — Transfers out of Level 3 (2,182 ) — (4,206 ) — — Fair value, end of period $ 21,145 $ 24,488 $ 41,666 $ 12,869 $ 3,346 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ 1,552 $ (487 ) $ 215 $ — $ — For the year ended December 31, 2016 (continued): Funds withheld at interest-embedded derivatives Other assets - longevity swaps Interest Other liabilities - mortality swaps Fair value, beginning of period $ (76,698 ) $ 14,996 $ (1,070,584 ) $ (2,619 ) Total gains/losses (realized/unrealized) Included in earnings, net: Investment related gains (losses), net 54,169 — 7,834 — Interest credited — — 10,709 — Included in other comprehensive income — (1,133 ) — — Other revenue — 13,095 — (172 ) Purchases (1) — — (12,725 ) — Sales (1) — — — — Settlements (1) — — 74,458 329 Fair value, end of period $ (22,529 ) $ 26,958 $ (990,308 ) $ (2,462 ) Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment related gains (losses), net $ 54,169 $ — $ (4,579 ) $ — Other revenue — 13,095 — (172 ) Interest credited — — (63,748 ) — For the year ended December 31, 2015: Fixed maturity securities - available-for-sale Corporate Canadian government RMBS ABS Fair value, beginning of period $ 1,310,427 $ — $ 188,094 $ 572,960 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (3,517 ) 2,788 (1,754 ) 4,526 Investment related gains (losses), net (2,814 ) — (216 ) 808 Included in other comprehensive income (32,452 ) 70,144 (944 ) (2,490 ) Purchases (1) 243,871 — 249,208 229,220 Sales (1) (3,949 ) — (985 ) (13,105 ) Settlements (1) (279,495 ) — (39,494 ) (98,918 ) Transfers into Level 3 15,455 343,144 2,853 13,542 Transfers out of Level 3 (20,556 ) — (66,113 ) (402,707 ) Fair value, end of period $ 1,226,970 $ 416,076 $ 330,649 $ 303,836 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ (3,396 ) $ 2,788 $ (1,753 ) $ 2,465 Investment related gains (losses), net (2,278 ) — — — For the year ended December 31, 2015 (continued): Fixed maturity securities - available-for-sale CMBS U.S. government State Other foreign government Fair value, beginning of period $ 86,746 $ 28,529 $ 42,711 $ 19,663 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses 2,817 (48 ) 32 — Investment related gains (losses), net (4,737 ) (233 ) (19 ) — Included in other comprehensive income (337 ) (602 ) (3,055 ) (7 ) Purchases (1) 42 544 — — Sales (1) (6,153 ) — — — Settlements (1) (7,226 ) (1,925 ) (492 ) (1,258 ) Transfers into Level 3 12,828 — — — Transfers out of Level 3 (15,417 ) — (835 ) (4,333 ) Fair value, end of period $ 68,563 $ 26,265 $ 38,342 $ 14,065 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ 2,718 $ (48 ) $ 32 $ — Investment related gains (losses), net (3,593 ) — — — For the year ended December 31, 2015 (continued): Funds withheld at interest-embedded derivatives Other invested Other assets - longevity swaps Interest Other liabilities - mortality swaps Fair value, beginning of period $ 22,094 $ 7,904 $ 7,727 $ (1,085,166 ) $ (797 ) Total gains/losses (realized/unrealized) Included in earnings, net: Investment related gains (losses), net (98,792 ) — — (33,191 ) — Interest credited — — — 19,440 — Included in other comprehensive income — (412 ) (959 ) — — Other revenue — — 8,228 — (1,822 ) Purchases (1) — 4,529 — (42,798 ) — Sales (1) — — — — — Settlements (1) — — — 71,131 — Transfers out of Level 3 — (12,021 ) — — — Fair value, end of period $ (76,698 ) $ — $ 14,996 $ (1,070,584 ) $ (2,619 ) Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment related gains (losses), net $ (98,792 ) $ — $ — $ (43,496 ) $ — Other revenue — — 8,228 — (1,822 ) Interest credited — — — (51,691 ) — (1) The amount reported within purchases, sales and settlements is the purchase price (for purchases) and the sales/settlement proceeds (for sales and settlements) based upon the actual date purchased or sold/settled. Items purchased and sold/settled in the same period are excluded from the rollforward. The Company had no issuances during the period.
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	For the year ended December 31, 2017: Fixed maturity securities - available-for-sale Corporate Canadian government RMBS ABS Fair value, beginning of period $ 1,272,253 $ 475,965 $ 160,291 $ 219,280 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (1,429 ) 13,180 (346 ) 1,776 Investment related gains (losses), net 4,991 — 729 245 Included in other comprehensive income (6,719 ) 104,797 2,341 7,044 Purchases (1) 408,995 — 76,792 45,215 Sales (1) (89,248 ) — (28,043 ) — Settlements (1) (285,958 ) — (18,988 ) (87,328 ) Transfers into Level 3 47,360 — 9,100 85,152 Transfers out of Level 3 (12,973 ) — (93,994 ) (147,910 ) Fair value, end of period $ 1,337,272 $ 593,942 $ 107,882 $ 123,474 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ (1,457 ) $ 13,180 $ (196 ) $ 669 Investment related gains (losses), net (5,389 ) — (346 ) — For the year ended December 31, 2017 (continued): Fixed maturity securities - available-for-sale CMBS U.S. government State Other foreign government Short-term investments Fair value, beginning of period $ 21,145 $ 24,488 $ 41,666 $ 12,869 $ 3,346 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses 709 (461 ) (55 ) (1 ) — Investment related gains (losses), net (595 ) — — — — Included in other comprehensive income (71 ) 19 (15 ) (252 ) 11 Purchases (1) — 465 — 496 3,703 Sales (1) (3,720 ) — — — — Settlements (1) (5,404 ) (2,000 ) (843 ) (672 ) (335 ) Transfers into Level 3 1,302 — 7,294 — — Transfers out of Level 3 (10,132 ) — (6,844 ) (7,348 ) (3,629 ) Fair value, end of period $ 3,234 $ 22,511 $ 41,203 $ 5,092 $ 3,096 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ — $ (461 ) $ (54 ) $ (1 ) $ — For the year ended December 31, 2017 (continued): Funds withheld at interest-embedded derivatives Other assets - longevity swaps Interest Other liabilities - mortality swaps Fair value, beginning of period $ (22,529 ) $ 26,958 $ (990,308 ) $ (2,462 ) Total gains/losses (realized/unrealized) Included in earnings, net: Investment related gains (losses), net 144,723 — 32,166 — Interest credited — — (80,062 ) — Included in other comprehensive income — 4,343 — — Other revenue — 9,358 — (921 ) Purchases (1) — — (55,237 ) — Sales (1) — — — — Settlements (1) — — 79,213 1,700 Fair value, end of period $ 122,194 $ 40,659 $ (1,014,228 ) $ (1,683 ) Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment related gains (losses), net $ 144,723 $ — $ 23,472 $ — Other revenue — 9,358 — (921 ) Interest credited — — (159,276 ) — For the year ended December 31, 2016: Fixed maturity securities - available-for-sale Corporate Canadian government RMBS ABS Fair value, beginning of period $ 1,226,970 $ 416,076 $ 330,649 $ 303,836 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (2,399 ) 12,197 (595 ) 801 Investment related gains (losses), net (4,756 ) — (2,153 ) 1,101 Included in other comprehensive income 10,022 47,692 (1,621 ) (2,696 ) Purchases (1) 312,720 — 103,553 138,522 Sales (1) (60,399 ) — (167,684 ) (38,681 ) Settlements (1) (195,016 ) — (38,495 ) (61,770 ) Transfers into Level 3 14,098 — 1,728 56,105 Transfers out of Level 3 (28,987 ) — (65,091 ) (177,938 ) Fair value, end of period $ 1,272,253 $ 475,965 $ 160,291 $ 219,280 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ (2,343 ) $ 12,197 $ (158 ) $ 734 Investment related gains (losses), net (817 ) — (231 ) — For the year ended December 31, 2016 (continued): Fixed maturity securities - available-for-sale CMBS U.S. government State Other foreign government Short-term investments Fair value, beginning of period $ 68,563 $ 26,265 $ 38,342 $ 14,065 $ — Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses 1,677 (487 ) 215 — — Investment related gains (losses), net (876 ) — — — — Included in other comprehensive income (5,887 ) 39 962 110 — Purchases (1) 1,545 508 6,952 — 3,365 Sales (1) (41,143 ) — — — — Settlements (1) (552 ) (1,837 ) (599 ) (1,306 ) (19 ) Transfers into Level 3 — — — — — Transfers out of Level 3 (2,182 ) — (4,206 ) — — Fair value, end of period $ 21,145 $ 24,488 $ 41,666 $ 12,869 $ 3,346 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ 1,552 $ (487 ) $ 215 $ — $ — For the year ended December 31, 2016 (continued): Funds withheld at interest-embedded derivatives Other assets - longevity swaps Interest Other liabilities - mortality swaps Fair value, beginning of period $ (76,698 ) $ 14,996 $ (1,070,584 ) $ (2,619 ) Total gains/losses (realized/unrealized) Included in earnings, net: Investment related gains (losses), net 54,169 — 7,834 — Interest credited — — 10,709 — Included in other comprehensive income — (1,133 ) — — Other revenue — 13,095 — (172 ) Purchases (1) — — (12,725 ) — Sales (1) — — — — Settlements (1) — — 74,458 329 Fair value, end of period $ (22,529 ) $ 26,958 $ (990,308 ) $ (2,462 ) Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment related gains (losses), net $ 54,169 $ — $ (4,579 ) $ — Other revenue — 13,095 — (172 ) Interest credited — — (63,748 ) — For the year ended December 31, 2015: Fixed maturity securities - available-for-sale Corporate Canadian government RMBS ABS Fair value, beginning of period $ 1,310,427 $ — $ 188,094 $ 572,960 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (3,517 ) 2,788 (1,754 ) 4,526 Investment related gains (losses), net (2,814 ) — (216 ) 808 Included in other comprehensive income (32,452 ) 70,144 (944 ) (2,490 ) Purchases (1) 243,871 — 249,208 229,220 Sales (1) (3,949 ) — (985 ) (13,105 ) Settlements (1) (279,495 ) — (39,494 ) (98,918 ) Transfers into Level 3 15,455 343,144 2,853 13,542 Transfers out of Level 3 (20,556 ) — (66,113 ) (402,707 ) Fair value, end of period $ 1,226,970 $ 416,076 $ 330,649 $ 303,836 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ (3,396 ) $ 2,788 $ (1,753 ) $ 2,465 Investment related gains (losses), net (2,278 ) — — — For the year ended December 31, 2015 (continued): Fixed maturity securities - available-for-sale CMBS U.S. government State Other foreign government Fair value, beginning of period $ 86,746 $ 28,529 $ 42,711 $ 19,663 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses 2,817 (48 ) 32 — Investment related gains (losses), net (4,737 ) (233 ) (19 ) — Included in other comprehensive income (337 ) (602 ) (3,055 ) (7 ) Purchases (1) 42 544 — — Sales (1) (6,153 ) — — — Settlements (1) (7,226 ) (1,925 ) (492 ) (1,258 ) Transfers into Level 3 12,828 — — — Transfers out of Level 3 (15,417 ) — (835 ) (4,333 ) Fair value, end of period $ 68,563 $ 26,265 $ 38,342 $ 14,065 Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment income, net of related expenses $ 2,718 $ (48 ) $ 32 $ — Investment related gains (losses), net (3,593 ) — — — For the year ended December 31, 2015 (continued): Funds withheld at interest-embedded derivatives Other invested Other assets - longevity swaps Interest Other liabilities - mortality swaps Fair value, beginning of period $ 22,094 $ 7,904 $ 7,727 $ (1,085,166 ) $ (797 ) Total gains/losses (realized/unrealized) Included in earnings, net: Investment related gains (losses), net (98,792 ) — — (33,191 ) — Interest credited — — — 19,440 — Included in other comprehensive income — (412 ) (959 ) — — Other revenue — — 8,228 — (1,822 ) Purchases (1) — 4,529 — (42,798 ) — Sales (1) — — — — — Settlements (1) — — — 71,131 — Transfers out of Level 3 — (12,021 ) — — — Fair value, end of period $ (76,698 ) $ — $ 14,996 $ (1,070,584 ) $ (2,619 ) Unrealized gains and losses recorded in earnings for the period relating to those Level 3 assets and liabilities that were still held at the end of the period Included in earnings, net: Investment related gains (losses), net $ (98,792 ) $ — $ — $ (43,496 ) $ — Other revenue — — 8,228 — (1,822 ) Interest credited — — — (51,691 ) — (1) The amount reported within purchases, sales and settlements is the purchase price (for purchases) and the sales/settlement proceeds (for sales and settlements) based upon the actual date purchased or sold/settled. Items purchased and sold/settled in the same period are excluded from the rollforward. The Company had no issuances during the period.
Fair Value Assets Measured On Nonrecurring Basis [Text Block]	Nonrecurring Fair Value Measurements The following table presents information for assets measured at estimated fair value on a nonrecurring basis during the periods presented and still held at the reporting dates (for example, when there is evidence of impairment). The estimated fair values for these assets were determined using significant unobservable inputs. Carrying Value After Measurement Net Investment Gains (Losses) At December 31, Years ended December 31, (dollars in thousands) 2017 2016 2017 2016 Limited partnership interests (1) $ 4,656 $ 6,192 $ (7,204 ) $ (9,277 ) Private equities (2) 106 — (531 ) — (1) The impaired limited partnership interests presented above were accounted for using the cost method. Impairments on these cost method investments were recognized at estimated fair value determined using the net asset values of the Company’s ownership interest as provided in the financial statements of the investees. The market for these investments has limited activity and price transparency. (2) The fair value of the Company’s private equity investments is based on external valuation models.
Financial Instruments Carrying Amounts And Estimated Fair Value [Table Text Block]	The following table presents the carrying amounts and estimated fair values of the Company’s financial instruments, which were not measured at fair value on a recurring basis, as of December 31, 2017 and December 31, 2016 (dollars in thousands).This table excludes any payables or receivables for collateral under repurchase agreements and other transactions. The estimated fair value of the excluded amount approximates carrying value as they equal the amount of cash collateral received/paid. Estimated Fair Fair Value Measurement Using: December 31, 2017: Carrying Value (1) Value Level 1 Level 2 Level 3 NAV Assets: Mortgage loans on real estate $ 4,400,533 $ 4,477,654 $ — $ — $ 4,477,654 $ — Policy loans 1,357,624 1,357,624 — 1,357,624 — — Funds withheld at interest 5,955,092 6,275,623 — — 6,275,623 — Cash and cash equivalents 946,736 946,736 946,736 — — — Short-term investments 42,558 42,558 42,558 — — — Other invested assets 690,198 718,282 28,540 67,778 286,839 335,125 Accrued investment income 392,721 392,721 — 392,721 — — Liabilities: Interest-sensitive contract liabilities $ 12,683,872 $ 12,917,243 $ — $ — $ 12,917,243 $ — Long-term debt 2,788,365 2,959,912 — — 2,959,912 — Collateral finance and securitization notes 783,938 722,145 — — 722,145 — December 31, 2016: Assets: Mortgage loans on real estate $ 3,775,522 $ 3,786,987 $ — $ — $ 3,786,987 $ — Policy loans 1,427,602 1,427,602 — 1,427,602 — — Funds withheld at interest 5,893,381 6,193,166 — — 6,193,166 — Cash and cash equivalents 862,117 862,117 862,117 — — — Short-term investments 32,469 32,469 32,469 — — — Other invested assets 477,132 510,640 26,294 55,669 131,904 296,773 Accrued investment income 347,173 347,173 — 347,173 — — Liabilities: Interest-sensitive contract liabilities $ 10,225,099 $ 10,234,544 $ — $ — $ 10,234,544 $ — Long-term debt 3,088,635 3,186,173 — — 3,186,173 — Collateral finance and securitization notes 840,700 745,805 — — 745,805 — (1) Carrying values presented herein may differ from those in the Company’s consolidated balance sheets because certain items within the respective financial statement captions may be measured at fair value on a recurring basis.

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2017
Reinsurance Disclosures [Abstract]
Ceded Credit Risk [Table Text Block]	The following table presents information for the Company’s ceded reinsurance receivable assets, including the respective amount and A.M. Best rating for each reinsurer representing in excess of five percent of the total as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Reinsurer A.M. Best Rating Amount % of Total Amount % of Total Reinsurer A A+ $ 301,478 38.6 % $ 240,894 35.2 % Reinsurer B A+ 203,898 26.1 183,881 26.9 Reinsurer C A 67,723 8.7 68,832 10.1 Reinsurer D A++ 40,592 5.2 36,202 5.3 Reinsurer E A+ 40,528 5.2 35,484 5.2 Other reinsurers 127,808 16.2 118,679 17.3 Total $ 782,027 100.0 % $ 683,972 100.0 %
Reinsurance Premium And Effect On Claims And Other Policy Benefits [Table Text Block]	The effect of reinsurance on net premiums is as follows (dollars in thousands): Years ended December 31, 2017 2016 2015 Direct $ 61,571 $ 57,562 $ 43,106 Reinsurance assumed 10,642,462 10,049,587 9,371,308 Reinsurance ceded (862,903 ) (858,278 ) (843,673 ) Net premiums $ 9,841,130 $ 9,248,871 $ 8,570,741 The effect of reinsurance on claims and other policy benefits as follows (dollars in thousands): Years ended December 31, 2017 2016 2015 Direct $ 104,447 $ 105,435 $ 82,942 Reinsurance assumed 9,281,590 8,621,647 8,205,308 Reinsurance ceded (867,120 ) (733,707 ) (798,868 ) Net claims and other policy benefits $ 8,518,917 $ 7,993,375 $ 7,489,382
Reinsurance Information [Table Text Block]	The effect of reinsurance on life insurance in force is shown in the following schedule (dollars in millions): Direct Assumed Ceded Net Assumed/Net % December 31, 2017 $ 1,462 $ 3,297,275 $ 205,529 $ 3,093,208 106.6 % December 31, 2016 1,576 3,062,525 214,727 2,849,374 107.5 December 31, 2015 1,686 2,995,079 222,388 2,774,377 108.0

Deferred Policy Acquisition C39

Deferred Policy Acquisition Costs (Tables)	12 Months Ended
	Dec. 31, 2017
Deferred Policy Acquisition Costs Disclosures [Abstract]
Deferred Policy Acquisition Costs [Table Text Block]	The following reflects the amounts of policy acquisition costs deferred and amortized (dollars in thousands): Years ended December 31, 2017 2016 2015 Balance, beginning of year $ 3,338,605 $ 3,392,437 $ 3,342,575 Capitalization 348,470 350,233 352,260 Amortization (including interest) (432,474 ) (341,115 ) (288,630 ) Change in value of embedded derivatives (70,392 ) (40,077 ) 58,754 Attributed to unrealized investment gains (losses) (8,220 ) (3,541 ) 17,510 Foreign currency translation 63,835 (19,332 ) (90,032 ) Balance, end of year $ 3,239,824 $ 3,338,605 $ 3,392,437

Income Tax (Tables)

Income Tax (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]	Pre-tax income for the years ended December 31, 2017, 2016 and 2015 consists of the following (dollars in thousands): 2017 2016 2015 Pre-tax income - U.S. $ 870,532 $ 758,496 $ 493,328 Pre-tax income - foreign 272,283 285,450 251,467 Total pre-tax income $ 1,142,815 $ 1,043,946 $ 744,795
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	The provision for income tax expense for the years ended December 31, 2017, 2016 and 2015 consists of the following (dollars in thousands): 2017 2016 2015 Current income tax expense (benefit): U.S. $ 131,108 $ 1,020 $ 1,588 Foreign 36,830 47,706 92,045 Total current 167,938 48,726 93,633 Deferred income tax expense (benefit): U.S. 159,853 273,928 193,204 U.S. Tax Reform provisional estimate (1,033,755 ) — — Foreign 26,598 19,849 (44,208 ) Total deferred (847,304 ) 293,777 148,996 Total provision for income taxes $ (679,366 ) $ 342,503 $ 242,629
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	U.S. federal income tax statutory rate of 35% as a result of the following for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): 2017 2016 2015 Tax provision at U.S. statutory rate $ 399,985 $ 365,381 $ 260,678 Increase (decrease) in income taxes resulting from: U.S. Tax Reform provisional estimate (1,033,755 ) — — Foreign tax rate differing from U.S. tax rate (21,867 ) (13,974 ) (9,950 ) Differences in tax basis in foreign jurisdictions (23,324 ) (17,770 ) (32,472 ) Deferred tax valuation allowance 29,458 10,963 19,157 Amounts related to audit contingencies (7,184 ) 111 88 Equity compensation excess benefit (10,532 ) — — Corporate rate changes (6,065 ) — — Subpart F for non-full inclusion companies 1,528 1,783 3,473 Foreign tax Credits (1,681 ) (1,683 ) (1,936 ) Return to provision Adjustments (4,674 ) (1,473 ) 1,482 Other, net (1,255 ) (835 ) 2,109 Total provision for income taxes $ (679,366 ) $ 342,503 $ 242,629 Effective tax rate (59.4 )% 32.8 % 32.6 %
Schedule Of Income Tax Expense Benefit Intraperiod Tax Allocation [Table Text Block]	Total income taxes for the years ended December 31, 2017, 2016 and 2015 were as follows (dollars in thousands): 2017 2016 2015 Provision for income taxes $ (679,366 ) $ 342,503 $ 242,629 Income tax from OCI and additional paid-in-capital: Net unrealized holding gain (loss) on debt and equity securities recognized for financial reporting purposes 306,849 157,929 (339,889 ) Exercise of stock options — (162 ) (2,963 ) Foreign currency translation (42,153 ) 21,081 16,478 Unrealized pension and post retirement 404 1,772 1,726 Total income taxes provided $ (414,266 ) $ 523,123 $ (82,019 )
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	The tax effects of temporary differences that give rise to significant portions of the deferred income tax assets and liabilities at December 31, 2017 and 2016 , are presented in the following tables (dollars in thousands): 2017 2016 Deferred income tax assets: Nondeductible accruals $ 80,905 $ 125,879 Differences between tax and financial reporting amounts concerning certain reinsurance transactions 96,043 87,688 Differences in the tax basis of cash and invested assets 557 775 Investment income differences 43,230 35,192 Deferred acquisition costs capitalized for tax 88,531 143,003 Net operating loss carryforward 535,374 325,806 Capital loss and tax credit carryforwards 102,143 101,223 Subtotal 946,783 819,566 Valuation allowance (226,884 ) (133,354 ) Total deferred income tax assets 719,899 686,212 Deferred income tax liabilities: Deferred acquisition costs capitalized for financial reporting 627,378 1,013,642 Differences between tax and financial reporting amounts concerning certain reinsurance transactions 1,547,101 1,773,929 Differences in the tax basis of cash and invested assets 674,569 505,841 Investment income differences 1,858 5,635 Differences in foreign currency translation 33,803 91,067 Prepaid expenses — — Total deferred income tax liabilities 2,884,709 3,390,114 Net deferred income tax liabilities $ 2,164,810 $ 2,703,902 Balance sheet presentation of net deferred income tax liabilities: Included in other assets $ 33,499 $ 66,738 Included in deferred income taxes 2,198,309 2,770,640 Net deferred income tax liabilities $ 2,164,810 $ 2,703,902
Summary of Income Tax Contingencies [Table Text Block]	A reconciliation of the beginning and ending amount of unrecognized tax benefits for the years ended December 31, 2017, 2016 and 2015 , is as follows (dollars in thousands): Total Unrecognized Tax Benefits 2017 2016 2015 Beginning balance, January 1 $ 297,290 $ 296,213 $ 274,661 Additions for tax positions of prior years 247,596 226,720 26,170 Reductions for tax positions of prior years (246,894 ) (229,719 ) (7,820 ) Additions for tax positions of current year 36,438 4,186 3,396 Settlements with tax authorities (13,206 ) (110 ) (194 ) Ending balance, December 31 $ 321,224 $ 297,290 $ 296,213

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Schedule of Changes in Projected Benefit Obligations [Table Text Block]	A December 31 measurement date is used for all of the defined benefit and postretirement plans. The status of these plans as of December 31, 2017 and 2016 is summarized below (dollars in thousands): December 31, Pension Benefits Other Benefits 2017 2016 2017 2016 Change in benefit obligation: Benefit obligation at beginning of year $ 161,955 $ 142,239 $ 60,524 $ 63,307 Service cost 10,686 10,319 2,543 2,883 Interest Cost 5,326 4,790 2,118 2,259 Participant contributions — — 354 305 Amendments (1) 159 — — (13,743 ) Actuarial (gains) losses 11,336 9,973 5,510 6,228 Settlement (gains) losses (438 ) 258 — — Settlements (12,907 ) (3,152 ) — — Benefits paid (5,974 ) (3,047 ) (851 ) (715 ) Foreign exchange translations and other adjustments 2,000 575 — — Benefit obligation at end of year $ 172,143 $ 161,955 $ 70,198 $ 60,524
Schedule of Changes in Fair Value of Plan Assets [Table Text Block]	December 31, Pension Benefits Other Benefits 2017 2016 2017 2016 Change in plan assets: Fair value of plan assets at beginning of year $ 84,770 $ 68,435 $ — $ — Actual return on plan assets 14,481 6,584 — — Employer contributions 22,866 15,950 497 410 Participant contributions — — 354 305 Disbursement for settlements (12,907 ) (3,152 ) — — Benefits paid and expenses (5,974 ) (3,047 ) (851 ) (715 ) Fair value of plan assets at end of year $ 103,236 $ 84,770 $ — $ — Funded status at end of year $ (68,907 ) $ (77,185 ) $ (70,198 ) $ (60,524 )
Schedule of Net Funded Status [Table Text Block]	December 31, Qualified Plans Non-Qualified Plans (1) Total 2017 2016 2017 2016 2017 2016 Aggregate fair value of plan assets $ 103,236 $ 84,770 $ — $ — $ 103,236 $ 84,770 Aggregate projected benefit obligations 107,072 96,418 65,071 65,537 172,143 161,955 Under funded $ (3,836 ) $ (11,648 ) $ (65,071 ) $ (65,537 ) $ (68,907 ) $ (77,185 ) (1) For non-qualified plans, there are no required funding levels.
Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	December 31, Pension Benefits Other Benefits 2017 2016 2017 2016 Amounts recognized in accumulated other comprehensive income: Net actuarial loss $ 40,058 $ 46,119 $ 35,672 $ 32,156 Net prior service cost (credit) 804 703 (11,806 ) (13,121 ) Total $ 40,862 $ 46,822 $ 23,866 $ 19,035
Schedule Of Projected Benefit Obligations In Excess Of Fair Value Of Plan Assets [Table Text Block]	The following table presents information for qualified and non-qualified pension plans with a projected benefit obligation in excess of plan assets as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Projected benefit obligation $ 172,143 $ 161,955 Fair value of plan assets 103,236 84,770
Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]	The following table presents information for pension plans with an accumulated benefit obligation in excess of plan assets as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Accumulated benefit obligation $ 169,705 $ 158,580 Fair value of plan assets 103,236 84,770
Schedule of Defined Benefit Plan Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	The components of net periodic benefit cost, included in other operating expenses on the consolidated statements of income, and other changes in plan assets and benefit obligations recognized in other comprehensive income were as follows (dollars in thousands): Pension Benefits Other Benefits 2017 2016 2015 2017 2016 2015 Net periodic benefit cost: Service cost $ 10,686 $ 10,319 $ 9,222 $ 2,543 $ 2,883 $ 4,062 Interest cost 5,326 4,790 5,035 2,118 2,259 2,572 Expected return on plan assets (6,215 ) (5,138 ) (4,897 ) — — — Amortization of prior actuarial losses 4,382 4,323 3,429 1,992 1,827 2,465 Amortization of prior service cost (credit) 344 294 309 (1,315 ) (622 ) — Settlements 4,785 1,026 — — — — Net periodic benefit cost 19,308 15,614 13,098 5,338 6,347 9,099 Other changes in plan assets and benefit obligations recognized in other comprehensive income: Net actuarial (gains) losses 2,633 8,785 5,774 5,507 6,228 (2,729 ) Amortization of actuarial (gains) losses (4,382 ) (4,323 ) (3,429 ) (1,992 ) (1,827 ) (2,465 ) Amortization of prior service cost (credit) (344 ) (294 ) (309 ) 1,315 622 — Settlements (4,785 ) (1,026 ) — — — — Prior service cost (credit) (1) 159 — — — (13,743 ) — Foreign exchange translations and other adjustments 759 707 (1,797 ) — — — Total recognized in other comprehensive income (5,960 ) 3,849 239 4,830 (8,720 ) (5,194 ) Total recognized in net periodic benefit cost and other comprehensive income $ 13,348 $ 19,463 $ 13,337 $ 10,168 $ (2,373 ) $ 3,905
Schedule of Expected Benefit Payments [Table Text Block]	The following benefit payments, which reflect expected future service as appropriate, are expected to be paid (dollars in thousands): Pension Benefits Other Benefits 2018 $ 9,315 $ 1,238 2019 9,765 1,495 2020 10,885 1,842 2021 11,102 2,188 2022 13,184 2,521 2023-2027 69,285 18,205
Schedule of Assumptions Used [Table Text Block]	Weighted average assumptions used to determine the accumulated benefit obligation and net benefit cost or income were as follows: Pension Benefits Other Benefits 2017 2016 2015 2017 2016 2015 Discount rate used to determine benefit obligation 3.40 % 3.80 % 3.99 % 3.56 % 4.10 % 4.43 % Discount rate used to determine net benefit cost or income 3.81 % 3.95 % 3.77 % 4.10 % 4.43 % 4.05 % Expected long-term rate of return on plan assets 7.35 % 7.35 % 7.35 % — % — % — % Rate of compensation increases 4.16 % 4.08 % 4.08 % — % — % — %
Schedule of Health Care Cost Trend Rates [Table Text Block]	The assumed health care cost trend rates used in measuring the accumulated non-pension post-retirement benefit obligation were as follows: December 31, 2017 2016 Pre-Medicare eligible claims 9% down to 5% in 2024 10% down to 5% in 2024 Medicare eligible claims 9% down to 5% in 2024 10% down to 5% in 2024
Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block]	A one-percentage point change in assumed health care cost trend rates would have the following effects (dollars in thousands): One Percent Increase One Percent Decrease Effect on total of service and interest cost components $ 7,941 $ (7,104 ) Effect on accumulated postretirement benefit obligation $ 447 $ (359 )
Schedule of Allocation of Plan Assets [Table Text Block]	The fair values of the Company’s qualified pension plan assets as of December 31, 2017 and 2016 are summarized below (dollars in thousands): December 31, 2017 Fair Value Measurement Using: Total Level 1 Level 2 Level 3 Mutual Funds (1) $ 103,106 $ 103,106 $ — $ — Cash 130 130 — — Total $ 103,236 $ 103,236 $ — $ — (1) Mutual funds were invested 27% in U.S. equity funds, 36% in U.S. fixed income funds, 22% in non-U.S. equity funds and 15% in other. December 31, 2016 Fair Value Measurement Using: Total Level 1 Level 2 Level 3 Mutual Funds (2) $ 84,671 $ 84,671 $ — $ — Cash 99 99 — — Total $ 84,770 $ 84,770 $ — $ — (2) Mutual funds were invested 28% in U.S. equity funds, 37% in U.S. fixed income funds, 20% in non-U.S. equity funds and 15% in other.

Financial Condition and Net I42

Financial Condition and Net Income on a Statutory Basis - Significant Subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2017
Statutory Basis [Abstract]
Statutory Accounting Practices Disclosure [Table Text Block]	Statutory net income, and capital and surplus of the Company’s insurance subsidiaries, determined in accordance with statutory accounting practices prescribed by the applicable state insurance department or local regulatory authority are as follows (dollars in thousands): Statutory Capital & Surplus Statutory Net Income (Loss) 2017 2016 2017 2016 2015 RGA Reinsurance (U.S.) $ 1,584,007 $ 1,521,644 $ 138,359 $ 148,576 $ (23,615 ) Reinsurance Company of Missouri 1,557,453 1,651,274 (183,136 ) 272,038 51,041 RGA Life Reinsurance Company of Canada 1,006,190 915,134 25,971 13,947 113,526 RGA Reinsurance Company (Barbados) Ltd. 1,278,006 957,051 309,346 95,859 113,049 RGA Australia 476,528 370,039 78,497 (7,694 ) (18,128 ) RGA Atlantic Reinsurance Company Ltd. 812,307 596,016 213,511 110,172 132,192 RGA Americas Reinsurance Company, Ltd. (1) 4,833,890 3,752,910 624,145 282,226 264,518 Other reinsurance subsidiaries 2,694,317 2,224,833 65,658 130,289 300,847 (1) In 2017, the Company contributed to RGA Americas Reinsurance Company, Ltd. all of the outstanding shares of its wholly-owned subsidiary, RGA Australia. Periods prior to 2017 have been adjusted to reflect this contribution.
Reconciliation Of NAIC SAP And Prescribed Practice [Text Block]	A reconciliation of the Company’s surplus between NAIC SAP and practices prescribed by the state of domicile is shown below (dollars in thousands): December 31, 2017 2016 Prescribed practice – surplus note $ 726,531 $ 574,574 Prescribed practice – letters of credit (960,100 ) (615,100 ) Surplus (deficit) – NAIC SAP $ (233,569 ) $ (40,526 )

Commitments Contingencies and43

Commitments Contingencies and Guarantees (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Fair Value, Off-balance Sheet Risks [Table Text Block]	The Company’s commitments to fund investments as of December 31, 2017 and 2016 are presented in the following table (dollars in thousands): 2017 2016 Limited partnership interests and joint ventures $ 485,197 $ 332,169 Commercial mortgage loans 40,815 126,248 Bank loans and private placements 60,472 58,318 Equity release mortgages 153,937 130,324
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	Future minimum office space annual rentals under non-cancelable operating leases at December 31, 2017 are as follows (dollars in thousands): Operating Leases 2018 $ 11,157 2019 7,108 2020 4,879 2021 3,076 2022 2,421 Thereafter 9,466
Other Commitments [Table Text Block]	The following table presents the maximum potential obligation for these commitments as of December 31, 2017 (dollars in millions): Commitment Period Maximum Potential Obligation 2023 $ 500.0 2033 450.0 2034 2,000.0 2035 1,314.2 2036 2,932.0 2037 5,750.0
Schedule of Guarantor Obligations [Table Text Block]	RGA’s guarantees issued as of December 31, 2017 and 2016 are reflected in the following table (dollars in thousands): 2017 2016 Treaty guarantees $ 1,047,449 $ 902,216 Treaty guarantees, net of assets in trust 926,393 780,786 Securities borrowing and repurchase arrangements 294,325 263,820 Financing arrangements 86,183 119,073 Lease obligations 1,662 2,428

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments [Table Text Block]	The Company’s long-term debt consists of the following as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 $300 million 5.625% Senior Notes due 2017 $ — $ 299,945 $400 million 6.45% Senior Notes due 2019 399,873 399,805 $400 million 5.00% Senior Notes due 2021 399,245 399,025 $400 million 4.70% Senior Notes due 2023 399,138 398,986 $400 million 3.95% Senior Notes due 2026 399,987 399,985 $100 million 4.09% Promissory Note due 2039 91,787 94,370 $400 million 6.20% Subordinated Debentures due 2042 400,000 400,000 $400 million 5.75% Subordinated Debentures due 2056 400,000 400,000 $400 million Variable Rate Junior Subordinated Debentures due 2065 318,740 318,737 Sub-total 2,808,770 3,110,853 Unamortized issuance costs (20,405 ) (22,218 ) Long-term Debt $ 2,788,365 $ 3,088,635
Schedule of Maturities of Long-term Debt [Table Text Block]	Future principal payments due on long-term debt, excluding discounts, as of December 31, 2017 , were as follows (dollars in thousands): Calendar Year 2018 2019 2020 2021 2022 Thereafter Long-term debt $ 2,690 $ 402,802 $ 2,919 $ 403,040 $ 3,167 $ 1,996,972
Schedule of Line of Credit Facilities [Table Text Block]	The following table provides additional information on the Company’s existing committed credit facilities as of December 31, 2017 and 2016 (dollars in thousands): Amount Utilized (1) December 31, Current Capacity Maturity Date 2017 2016 Basis of Fees $180,403 (2) November 2018 $ 8,638 $ 31,382 Fixed 5,952 (2) March 2019 5,952 17,513 Fixed 850,000 September 2019 96,564 96,095 Senior unsecured long-term debt rating 188,000 October 2019 188,000 270,000 Fixed 117,135 (2) December 2019 117,135 72,080 Fixed 100,000 June 2020 75,573 70,690 Fixed 100,000 May 2021 100,000 — Fixed 75,000 June 2021 61,900 85,040 Fixed 500,000 May 2022 500,000 — Fixed (1) Represents issued but undrawn letters of credit. There was no cash borrowed for the periods presented. (2) Foreign currency denominated facility, amounts presented are in U.S. dollars.

Collateral Finance and Securi45

Collateral Finance and Securitization Notes Collateral Finance and Securitization Notes (Tables)	12 Months Ended
	Dec. 31, 2017
Collateralized Financings [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]	The Company’s collateral finance and securitization notes consist of the following as of December 31, 2017 and 2016 (dollars in thousands): 2017 2016 Timberlake Financial $ 411,951 $ 451,880 RGA Barbados 159,100 148,820 Chesterfield Financial 217,800 246,300 Unamortized issuance costs (4,913 ) (6,300 ) Total $ 783,938 $ 840,700

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Reconciliation of Revenue from Segments to Consolidated [Table Text Block]	For the years ended December 31, 2017 2016 2015 Revenues: U.S. and Latin America: Traditional $ 6,100,171 $ 5,964,968 $ 5,465,026 Financial Solutions 1,150,378 840,446 643,865 Total 7,250,549 6,805,414 6,108,891 Canada: Traditional 1,103,520 1,118,004 1,023,012 Financial Solutions 48,938 46,938 45,034 Total 1,152,458 1,164,942 1,068,046 Europe, Middle East and Africa: Traditional 1,362,075 1,195,149 1,190,742 Financial Solutions 311,071 340,518 286,666 Total 1,673,146 1,535,667 1,477,408 Asia Pacific: Traditional 2,210,686 1,771,150 1,638,357 Financial Solutions 73,775 63,382 56,581 Total 2,284,461 1,834,532 1,694,938 Corporate and Other 155,155 180,956 68,895 Total $ 12,515,769 $ 11,521,511 $ 10,418,178
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block]	For the years ended December 31, 2017 2016 2015 Income (loss) before income taxes: U.S. and Latin America: Traditional $ 373,434 $ 371,101 $ 235,771 Financial Solutions 401,584 283,380 207,963 Total 775,018 654,481 443,734 Canada: Traditional 120,218 134,705 124,175 Financial Solutions 16,643 7,945 13,902 Total 136,861 142,650 138,077 Europe, Middle East and Africa: Traditional 70,486 30,059 48,410 Financial Solutions 123,514 138,007 108,445 Total 194,000 168,066 156,855 Asia Pacific: Traditional 148,786 113,928 105,654 Financial Solutions 13,130 4,063 19,619 Total 161,916 117,991 125,273 Corporate and Other (124,980 ) (39,242 ) (119,144 ) Total $ 1,142,815 $ 1,043,946 $ 744,795
Reconciliation of Other Significant Reconciling Items from Segments to Consolidated [Table Text Block]	For the years ended December 31, 2017 2016 2015 Interest expense: Corporate and Other $ 146,025 $ 137,623 $ 142,863 Total $ 146,025 $ 137,623 $ 142,863 For the years ended December 31, 2017 2016 2015 Depreciation and amortization: U.S. and Latin America: Traditional $ 284,959 $ 271,732 $ 218,974 Financial Solutions 208,790 155,560 44,275 Total 493,749 427,292 263,249 Canada: Traditional 24,057 22,170 23,887 Financial Solutions 10 11 — Total 24,067 22,181 23,887 Europe, Middle East and Africa: Traditional 35,000 46,562 60,193 Financial Solutions 91 72 — Total 35,091 46,634 60,193 Asia Pacific: Traditional 114,333 45,562 31,955 Financial Solutions 1,448 1,492 217 Total 115,781 47,054 32,172 Corporate and Other 37,276 13,894 16,495 Total $ 705,964 $ 557,055 $ 395,996 The table above includes amortization of DAC, including the effect from investment related gains and losses.
Reconciliation of Assets from Segment to Consolidated [Table Text Block]	For the years ended December 31, 2017 2016 Assets: U.S. and Latin America: Traditional $ 18,603,423 $ 18,140,825 Financial Solutions 15,959,206 13,712,106 Total 34,562,629 31,852,931 Canada: Traditional 4,161,452 3,846,682 Financial Solutions 126,372 85,405 Total 4,287,824 3,932,087 Europe, Middle East and Africa: Traditional 3,099,495 2,559,124 Financial Solutions 5,274,993 3,876,131 Total 8,374,488 6,435,255 Asia Pacific: Traditional 4,915,442 3,968,081 Financial Solutions 1,198,585 676,281 Total 6,114,027 4,644,362 Corporate and Other 7,175,850 6,233,244 Total $ 60,514,818 $ 53,097,879

Short-Duration Contracts (Table

Short-Duration Contracts (Tables)	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Short-duration Insurance Contracts, Claims Development [Table Text Block]	U.S. and Latin America As of (in thousands) December 31, 2017 Incurred Claims and Allocated Claim Adjustments, Net of Reinsurance (1) Total of Incurred-but-Not-Reported Liabilities Plus Expected Development on Reported Claims For the Years Ended December 31, Accident Year 2012 2013 2014 2015 2016 2017 2012 $ 322,579 $ 309,119 $ 297,037 $ 298,262 $ 299,098 $ 297,688 $ 24 2013 349,262 332,907 338,977 336,552 336,436 164 2014 407,953 411,373 396,383 397,151 1,597 2015 459,524 460,917 465,167 3,809 2016 500,843 499,785 23,149 2017 485,442 200,109 Total $ 2,481,669 Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net of Reinsurance (1) For the Years Ended December 31, Accident Year 2012 2013 2014 2015 2016 2017 2012 $ 109,323 $ 222,139 $ 243,890 $ 252,018 $ 258,297 $ 263,565 2013 114,457 248,828 277,130 285,817 292,067 2014 128,813 304,578 337,081 349,078 2015 146,196 360,658 407,282 2016 184,940 392,517 2017 189,853 Total $ 1,894,362 All outstanding claims prior to 2012, net of reinsurance 208,874 Liabilities for claims and claim adjustment expense, net of reinsurance $ 796,181 (1) 2012-2016 Unaudited. Asia Pacific As of (in thousands) December 31, 2017 Incurred Claims and Allocated Claim Adjustments, Net of Reinsurance (1) Total of Incurred-but-Not-Reported Liabilities Plus Expected Development on Reported Claims For the Years Ended December 31, Accident Year 2012 2013 2014 2015 2016 2017 2012 $ 230,295 $ 309,090 $ 313,862 $ 317,536 $ 325,992 $ 336,901 $ 13,196 2013 324,334 346,886 336,531 333,639 347,865 21,310 2014 306,919 332,718 294,049 300,025 27,113 2015 308,517 284,871 277,166 44,713 2016 252,197 228,342 62,959 2017 235,146 140,159 Total $ 1,725,445 Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net of Reinsurance (1) For the Years Ended December 31, Accident Year 2012 2013 2014 2015 2016 2017 2012 $ 54,638 $ 149,912 $ 205,303 $ 247,028 $ 269,808 $ 287,941 2013 55,175 159,799 231,919 261,359 289,472 2014 38,241 150,295 196,570 228,405 2015 54,241 131,364 185,393 2016 42,440 108,310 2017 39,262 Total $ 1,138,783 All outstanding claims prior to 2012, net of reinsurance 144,984 Liabilities for claims and claim adjustment expense, net of reinsurance $ 731,646 (1) 2012-2016 Unaudited.
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block]	The reconciliation of the net incurred and paid claims development tables to the liability for claims and claim adjustment expense in the consolidated balance sheets as of December 31, 2017 and 2016 , are as follows: 2017 Liabilities for claims and claim adjustment expense, net of reinsurance: U.S. and Latin America $ 796,181 Asia Pacific 731,646 Liabilities for claims and claim adjustment expense, net of reinsurance 1,527,827 Adjustments to reconcile to total policy claims and future policy benefits: Reinsurance recoverable 17,940 Effect of discounting and unallocated claims adjustment expense (146,331 ) Total adjustments (128,391 ) Other short-duration contracts: Canada 150,248 Europe, Middle East and Africa 346,916 Other 122,690 Total short-duration contracts 2,019,290 Other than short-duration contracts 25,336,025 Total future policy benefits and other policy claims and benefits $ 27,355,315
Short-duration Insurance Contracts, Schedule of Historical Claims Duration [Table Text Block]	The following is unaudited supplementary information about average historical claims duration as of December 31, 2017 : Average Annual Payout of Incurred Claims by Age, Net of Reinsurance Years 1 2 3 4 5 6 U.S. and Latin America 35.1 % 41.9 % 8.5 % 2.8 % 2.0 % 1.8 % Asia Pacific 16.5 % 30.3 % 18.0 % 10.5 % 7.6 % 5.4 %

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule Of Earnings Per Share Basic And Diluted By Common Class [Table Text Block]	The following table sets forth the computation of basic and diluted earnings per share on net income (in thousands, except per share information): 2017 2016 2015 Earnings: Net income (numerator for basic and diluted calculations) $ 1,822,181 $ 701,443 $ 502,166 Shares: Weighted average outstanding shares (denominator for basic calculations) 64,427 64,274 66,553 Equivalent shares from outstanding stock options 1,326 715 739 Diluted shares (denominator for diluted calculations) 65,753 64,989 67,292 Earnings per share: Basic $ 28.28 $ 10.91 $ 7.55 Diluted 27.71 10.79 7.46

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Schedule of Stock by Class [Table Text Block]	The changes in number of common stock shares, issued, held in treasury and outstanding are as follows for the periods indicated: Issued Held In Treasury Outstanding Balance, December 31, 2014 79,137,758 10,364,797 68,772,961 Common Stock acquired — 4,145,440 (4,145,440 ) Stock-based compensation (1) — (577,005 ) 577,005 Balance, December 31, 2015 79,137,758 13,933,232 65,204,526 Common Stock acquired — 1,356,892 (1,356,892 ) Stock-based compensation (1) — (454,868 ) 454,868 Balance, December 31, 2016 79,137,758 14,835,256 64,302,502 Common Stock acquired — 208,680 (208,680 ) Stock-based compensation (1) — (358,273 ) 358,273 Balance, December 31, 2017 79,137,758 14,685,663 64,452,095 (1) Represents net shares issued from treasury pursuant to the Company’s stock-based compensation programs.
Schedule of Comprehensive Income (Loss) [Table Text Block]	Accumulated other comprehensive income (loss) The following table presents the components of the Company’s other comprehensive income (loss) for the years ended December 31, 2017, 2016 and 2015 (dollars in thousands): For the year ended December 31, 2017 : Before-Tax Amount Tax (Expense) Benefit After-Tax Amount Foreign currency translation adjustments: Change arising during year $ 74,926 $ 25,369 $ 100,295 Foreign currency swap (47,953 ) 16,784 (31,169 ) Net foreign currency translation adjustments 26,973 42,153 69,126 Unrealized gains on investments: (1) Unrealized net holding gains arising during the year 1,029,591 (313,729 ) 715,862 Less: Reclassification adjustment for net gains realized in net income 25,039 (7,011 ) 18,028 Net unrealized gains 1,004,552 (306,718 ) 697,834 Change in unrealized OTTI on fixed maturity securities 375 (131 ) 244 Unrealized pension and postretirement benefits: Net prior service cost arising during the year 11,717 (4,095 ) 7,622 Net gain arising during the period (10,587 ) 3,691 (6,896 ) Unrealized pension and postretirement benefits, net 1,130 (404 ) 726 Other comprehensive income (loss) $ 1,033,030 $ (265,100 ) $ 767,930 For the year ended December 31, 2016 : Before-Tax Amount Tax (Expense) Benefit After-Tax Amount Foreign currency translation adjustments: Change arising during year $ 39,925 $ (24,663 ) $ 15,262 Foreign currency swap (10,234 ) 3,582 (6,652 ) Net foreign currency translation adjustments 29,691 (21,081 ) 8,610 Unrealized gains on investments: (1) Unrealized net holding gains arising during the year 641,606 (180,448 ) 461,158 Less: Reclassification adjustment for net gains realized in net income 65,798 (23,029 ) 42,769 Net unrealized gains 575,808 (157,419 ) 418,389 Change in unrealized OTTI on fixed maturity securities 1,457 (510 ) 947 Unrealized pension and postretirement benefits: Net prior service cost arising during the year 444 (149 ) 295 Net gain arising during the period 4,427 (1,623 ) 2,804 Unrealized pension and postretirement benefits, net 4,871 (1,772 ) 3,099 Other comprehensive income (loss) $ 611,827 $ (180,782 ) $ 431,045 For the year ended December 31, 2015: Before-Tax Amount Tax (Expense) Benefit After-Tax Amount Foreign currency translation adjustments: Change arising during year $ (342,539 ) $ 17,129 $ (325,410 ) Foreign currency swap 96,019 (33,607 ) 62,412 Net foreign currency translation adjustments (246,520 ) (16,478 ) (262,998 ) Unrealized losses on investments: (1) Unrealized net holding losses arising during the year (1,084,732 ) 359,407 (725,325 ) Less: Reclassification adjustment for net losses realized in net income (55,767 ) 19,518 (36,249 ) Net unrealized losses (1,028,965 ) 339,889 (689,076 ) Unrealized pension and postretirement benefits: Net prior service cost arising during the year 337 (107 ) 230 Net loss arising during the period 4,618 (1,619 ) 2,999 Unrealized pension and postretirement benefits, net 4,955 (1,726 ) 3,229 Other comprehensive income (loss) $ (1,270,530 ) $ 321,685 $ (948,845 ) (1) Includes cash flow hedges. See Note 5 f
Components Of Accumulated Other Comprehensive Income [Table Text Block]	A summary of the components of net unrealized appreciation (depreciation) of balances carried at fair value is as follows (dollars in thousands): For the years ended December 31, 2017 2016 2015 Change in net unrealized appreciation (depreciation) on: Fixed maturity securities available-for-sale $ 987,570 $ 561,906 $ (1,055,458 ) Other investments (1) 25,577 18,900 8,983 Effect on unrealized appreciation on: Deferred policy acquisition costs (8,220 ) (3,541 ) 17,510 Net unrealized appreciation (depreciation) $ 1,004,927 $ 577,265 $ (1,028,965 ) (1) Includes cash flow hedges. See Note 5 for additional information on cash flow hedges.
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The balance of and changes in each component of AOCI were as follows (dollars in thousands): Accumulated Currency Translation Adjustments Unrealized Appreciation (Depreciation) of Investments (1) Pension and Postretirement Benefits Accumulated Other Comprehensive Income (Loss) Balance, December 31, 2014 $ 81,847 $ 1,624,773 $ (49,491 ) $ 1,657,129 OCI before reclassifications (246,520 ) (1,101,760 ) (1,248 ) (1,349,528 ) Amounts reclassified from AOCI — 72,795 6,203 78,998 Deferred income tax benefit (expense) (16,478 ) 339,889 (1,726 ) 321,685 Balance, December 31, 2015 (181,151 ) 935,697 (46,262 ) 708,284 OCI before reclassifications 29,691 646,887 (951 ) 675,627 Amounts reclassified from AOCI — (69,622 ) 5,822 (63,800 ) Deferred income tax benefit (expense) (21,081 ) (157,929 ) (1,772 ) (180,782 ) Balance, December 31, 2016 (172,541 ) 1,355,033 (43,163 ) 1,139,329 OCI before reclassifications 26,973 1,039,387 (4,273 ) 1,062,087 Amounts reclassified from AOCI — (34,460 ) 5,403 (29,057 ) Deferred income tax benefit (expense) 42,153 (306,849 ) (404 ) (265,100 ) Adoption of new accounting standard 17,065 147,550 (8,243 ) 156,372 Balance, December 31, 2017 $ (86,350 ) $ 2,200,661 $ (50,680 ) $ 2,063,631 (1) Includes cash flow hedges of $2,619 , $(2,496) and $(29,397) as of December 31, 2017, 2016 and 2015 , respectively. See Note 5 for additional information on cash flow hedges.
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The following table presents the amounts of AOCI reclassifications for the years ended December 31, 2017 and 2016 (dollars in thousands): Amount Reclassified from AOCI Details about AOCI Components 2017 2016 Affected Line Item in Statement of Income Net unrealized investment gains (losses): Net unrealized gains and losses on available-for-sale securities $ 25,039 $ 65,798 Investment related gains (losses), net OTTI on fixed maturity securities — 74 Investment related gains (losses), net Cash flow hedges - Interest rate (79 ) — (1) Cash flow hedges - Currency/Interest rate 380 510 (1) Cash flow hedges - Forward bond purchase commitments 900 (301 ) (1) Deferred policy acquisition costs attributed to unrealized gains and losses 8,220 3,541 (2) Total 34,460 69,622 Provision for income taxes (10,308 ) (17,672 ) Net unrealized gains (losses), net of tax $ 24,152 $ 51,950 Amortization of defined benefit plan items: Prior service cost (credit) $ 971 $ 328 (3) Actuarial gains/(losses) (6,374 ) (6,150 ) (3) Total (5,403 ) (5,822 ) Provision for income taxes 1,891 2,038 Amortization of defined benefit plans, net of tax $ (3,512 ) $ (3,784 ) Total reclassifications for the period $ 20,640 $ 48,166 (1) See Note 5 for information on cash flow hedges. (2) See Note 8 for information on deferred policy acquisition costs. (3) See Note 10 for information on employee benefit plans.

Equity Based Compensation (Tabl

Equity Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]	Number of Options Weighted-Average Exercise Price Aggregate Intrinsic Value (in millions) Outstanding December 31, 2016 2,573,223 $ 68.70 Granted 171,388 $ 129.72 Exercised (430,429 ) $ 58.07 Forfeited (4,413 ) $ 87.15 Outstanding December 31, 2017 2,309,769 $ 75.17 $ 186.5 Options exercisable 1,700,629 $ 66.04 $ 152.9
Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]	Options Outstanding Options Exercisable Range of Exercise Prices Number Outstanding as of 12/31/2017 Weighted-Average Remaining Contractual Life (years) Weighted- Average Exercise Price Number Exercisable as of 12/31/2017 Weighted-Average Exercise Price $0.00 - $49.99 245,264 1.7 $ 40.54 245,264 $ 40.54 $50.00 - $59.99 902,246 4.4 $ 58.23 902,246 $ 58.23 $60.00 - $69.99 839 5.2 $ 60.24 839 $ 60.24 $70.00 - $79.99 190,137 6.2 $ 78.48 190,137 $ 78.48 $90.00 + 971,283 8.1 $ 99.02 362,143 $ 96.22 Totals 2,309,769 5.8 $ 75.17 1,700,629 $ 66.04
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	The following table presents the weighted average assumptions used to determine the fair value of stock options issued: For the years ended December 31, 2017 2016 2015 Dividend yield 1.26 % 1.58 % 1.47 % Risk-free rate of return 2.32 % 1.69 % 2.04 % Expected volatility 22.8 % 28.1 % 35.0 % Expected life (years) 7.0 7.0 7.0 Weighted average exercise price of stock options granted $ 129.72 $ 93.53 $ 91.65 Weighted average fair value of stock options granted $ 31.57 $ 24.52 $ 30.50
Share-based Compensation, Activity [Table Text Block]	The following table presents a summary of Performance Share and Restricted Stock Unit activity: Performance Contingent Units Restricted Stock Units Outstanding December 31, 2016 585,971 96,628 Granted 115,176 22,971 Paid (137,083 ) (38,843 ) Forfeited (100,805 ) (3,398 ) Outstanding December 31, 2017 463,259 77,358

Quarterly Results of Operatio51

Quarterly Results of Operations (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information [Table Text Block]	QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) Years Ended December 31, (in thousands, except per share data) 2017 First Second Third Fourth Total Revenues $ 3,008,740 $ 3,129,276 $ 3,145,310 $ 3,232,443 Total benefits and expenses 2,800,896 2,789,961 2,805,148 2,976,949 Income before income taxes 207,844 339,315 340,162 255,494 Net Income 145,512 232,190 227,591 1,216,888 Earnings Per Share: Basic earnings per share $ 2.26 $ 3.60 $ 3.53 $ 18.89 Diluted earnings per share 2.22 3.54 3.47 18.49 2016 First Second Third Fourth Total Revenues $ 2,512,568 $ 3,039,068 $ 2,900,577 $ 3,069,298 Total benefits and expenses 2,404,988 2,685,845 2,612,977 2,773,755 Income before income taxes 107,580 353,223 287,600 295,543 Net Income 76,472 236,103 198,719 190,149 Earnings Per Share: Basic earnings per share $ 1.18 $ 3.68 $ 3.10 $ 2.96 Diluted earnings per share 1.17 3.64 3.07 2.92

Summary of Investments Other 52

Summary of Investments Other Than Investments in Related Parties (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of Investments, Other than Investments in Related Parties [Abstract]
Summary Of Investments Other Than Investments In Related Parties [Table Text Block]	REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE I-SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES December 31, 2017 (in millions) Type of Investment Cost Fair Value Amount at Which Shown in the Balance Sheets (1) Fixed maturity securities: Bonds: United States government and government agencies and authorities $ 1,953 $ 1,944 $ 1,944 State and political subdivisions 648 703 703 Foreign governments (2) 6,098 7,621 7,621 Public utilities 2,454 2,649 2,649 Mortgage-backed and asset-backed securities 4,615 4,672 4,672 All other corporate bonds 19,513 20,562 20,562 Total fixed maturity securities 35,281 38,151 38,151 Equity securities: Non-redeemable preferred stock 42 40 40 Other equity securities 61 60 60 Total equity securities 103 100 100 Mortgage loans on real estate 4,401 4,401 Policy loans 1,358 1,358 Funds withheld at interest 6,083 6,083 Short-term investments 93 93 Other invested assets 1,505 1,505 Total investments $ 48,824 $ 51,691 (1) Fixed maturity securities are classified as available-for-sale and carried at fair value. (2) Includes fixed maturities directly issued by foreign governments, supranational and foreign government-sponsored enterprises.

Condensed Financial Informati53

Condensed Financial Information of The Registrant (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Financial Statements [Table Text Block]	2017 2016 2015 CONDENSED BALANCE SHEETS Assets: Fixed maturity securities available-for-sale, at fair value $ 710,303 $ 1,154,559 Short-term and other investments 54,517 245,478 Cash and cash equivalents 15,176 43,718 Investment in subsidiaries 12,043,911 9,209,700 Loans to subsidiaries 1,010,000 1,050,000 Other assets 234,707 258,379 Total assets $ 14,068,614 $ 11,961,834 Liabilities and stockholders’ equity: Long-term debt - unaffiliated (1) $ 2,775,579 $ 3,073,249 Long-term debt - affiliated (2) 500,000 500,000 Other liabilities 1,223,500 1,295,503 Stockholders’ equity 9,569,535 7,093,082 Total liabilities and stockholders’ equity $ 14,068,614 $ 11,961,834 CONDENSED STATEMENTS OF INCOME Interest / dividend income (3) $ 131,067 $ 602,830 $ 321,645 Investment related gains (losses), net (5,187 ) 203 (324 ) Operating expenses (20,517 ) (20,742 ) (13,652 ) Interest expense (177,417 ) (168,924 ) (176,364 ) Income (loss) before income tax and undistributed earnings of subsidiaries (72,054 ) 413,367 131,305 Income tax expense (benefit) 65,882 (23,911 ) (19,465 ) Net income (loss) before undistributed earnings of subsidiaries (137,936 ) 437,278 150,770 Equity in undistributed earnings of subsidiaries 1,960,117 264,165 351,396 Net income 1,822,181 701,443 502,166 Other comprehensive income (loss) (7,672 ) 5,531 44,073 Total comprehensive income $ 1,814,509 $ 706,974 $ 546,239 The condensed financial information of RGA (the “Parent Company”) should be read in conjunction with the consolidated financial statements of RGA and its subsidiaries and the notes thereto (the “Consolidated Financial Statements”). These condensed unconsolidated financial statements reflect the results of operations, financial position and cash flows for RGA. Investments in subsidiaries are accounted for using the equity method of accounting. (1) Long-term debt - unaffiliated consists of the following: 2017 2016 $300 million 5.625% Senior Notes due 2017 $ — $ 299,945 $400 million 6.45% Senior Notes due 2019 399,873 399,805 $400 million 5.00% Senior Notes due 2021 399,245 399,025 $400 million 4.70% Senior Notes due 2023 399,138 398,986 $400 million 3.95% Senior Notes due 2026 399,987 399,985 $400 million 6.20% Subordinated Debentures due 2042 400,000 400,000 $400 million 5.75% Subordinated Debentures due 2056 400,000 400,000 $400 million Variable Rate Junior Subordinated Debentures due 2065 398,670 398,667 Subtotal 2,796,913 3,096,413 Unamortized debt issue costs (21,334 ) (23,164 ) Total $ 2,775,579 $ 3,073,249 Repayments of long-term debt—unaffiliated due over the next five years total $400,000 in 2019 and $400,000 in 2021. (2) Long-term debt—affiliated in 2017 and 2016 and consists of $500,000 of subordinated debt issued to various operating subsidiaries. (3) Interest/Dividend income includes $478,602 and $196,445 of cash dividends received from consolidated subsidiaries in 2016 and 2015, respectively. In 2017 there were no cash dividends received from consolidated subsidiaries. REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE II—CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT (continued) December 31, (dollars in thousands) 2017 2016 2015 CONDENSED STATEMENTS OF CASH FLOWS Operating activities: Net income $ 1,822,181 $ 701,443 $ 502,166 Equity in earnings of subsidiaries (1,960,117 ) (264,165 ) (351,396 ) Other, net 57,677 (63,795 ) 486,159 Net cash (used in) provided by operating activities (80,259 ) 373,483 636,929 Investing activities: Sales of fixed maturity securities available-for-sale 514,508 228,383 100,734 Purchases of fixed maturity securities available-for-sale (75,000 ) (984,397 ) (52,698 ) Repayments/issuances of loans to subsidiaries 40,000 20,000 (10,000 ) Purchase of a business, net of cash acquired of $529 — — (3,701 ) Change in short-term investments — 102,508 (102,508 ) Change in other invested assets 125,506 (109,914 ) (7,542 ) Capital contributions to subsidiaries (62,500 ) (314,142 ) (103,832 ) Net cash (used in) provided by investing activities 542,514 (1,057,562 ) (179,547 ) Financing activities: Dividends to stockholders (117,291 ) (100,371 ) (93,381 ) Purchases of treasury stock (43,508 ) (122,916 ) (384,519 ) Exercise of stock options, net 7,292 15,321 11,151 Net change in cash collateral for loaned securities (37,290 ) 105,093 — Principal payments on debt (300,000 ) — — Proceeds from unaffiliated long-term debt issuance — 799,984 — Debt issuance costs — (8,766 ) — Net cash (used in) provided by financing activities (490,797 ) 688,345 (466,749 ) Net change in cash and cash equivalents (28,542 ) 4,266 (9,367 ) Cash and cash equivalents at beginning of year 43,718 39,452 48,819 Cash and cash equivalents at end of year $ 15,176 $ 43,718 $ 39,452 Supplementary information: Cash paid for interest $ 185,554 $ 169,860 $ 165,775 Cash paid for income taxes, net of refunds $ 8,248 $ 1,500 $ (120,680 )

Supplementary Insurance Infor54

Supplementary Insurance Information (Tables)	12 Months Ended
	Dec. 31, 2017
Supplementary Insurance Information [Abstract]
Supplementary Insurance Information For Insurance Companies Disclosure [Table Text Block]	REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE III—SUPPLEMENTARY INSURANCE INFORMATION (dollars in thousands) As of December 31, Deferred Policy Acquisition Costs Future Policy Benefits and Interest-Sensitive Contract Liabilities Other Policy Claims and Benefits Payable 2017 U.S. and Latin America operations: Traditional operations $ 1,818,572 $ 11,343,921 $ 1,814,018 Financial Solutions operations 405,623 15,127,529 17,876 Canada operations: Traditional operations 212,345 3,041,790 206,655 Financial Solutions operations — 27,908 1,040 Europe, Middle East and Africa operations: Traditional operations 229,150 1,075,786 882,744 Financial Solutions operations — 4,741,983 38,044 Asia Pacific operations: Traditional operations 552,947 1,611,633 2,017,920 Financial Solutions operations 21,187 1,118,012 6,885 Corporate and Other — 502,321 6,892 Total $ 3,239,824 $ 38,590,883 $ 4,992,074 2016 U.S. and Latin America operations: Traditional operations $ 1,818,211 $ 10,990,560 $ 1,659,473 Financial Solutions operations 582,031 13,074,231 20,352 Canada operations: Traditional operations 201,149 2,713,510 200,246 Financial Solutions operations — 29,531 4,599 Europe, Middle East and Africa operations: Traditional operations 206,837 913,351 740,218 Financial Solutions operations — 3,457,196 46,761 Asia Pacific operations: Traditional operations 512,123 1,288,642 1,563,707 Financial Solutions operations 18,254 641,614 19,643 Corporate and Other — 502,292 8,027 Total $ 3,338,605 $ 33,610,927 $ 4,263,026 REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE III—SUPPLEMENTARY INSURANCE INFORMATION (continued) (dollars in thousands) Year ended December 31, Premium Income Net Investment Income Policyholder Benefits and Interest Credited Amortization of DAC Other Operating Expenses 2017 U.S. and Latin America operations: Traditional operations $ 5,356,321 $ 728,073 $ 4,842,412 $ 191,725 $ 692,600 Financial Solutions operations 23,683 778,473 458,368 185,280 105,146 Canada operations: Traditional operations 901,976 189,018 757,912 12,426 212,964 Financial Solutions operations 38,229 5,115 29,639 — 2,656 Europe, Middle East and Africa operations: Traditional operations 1,301,640 55,511 1,096,211 20,570 174,808 Financial Solutions operations 163,720 123,258 153,874 — 33,683 Asia Pacific operations: Traditional operations 2,053,029 91,675 1,635,728 91,477 334,695 Financial Solutions operations 2,419 34,529 40,467 1,388 18,790 Corporate and Other 113 148,999 6,346 — 273,789 Total $ 9,841,130 $ 2,154,651 $ 9,020,957 $ 502,866 $ 1,849,131 2016 U.S. and Latin America operations: Traditional operations $ 5,249,571 $ 699,833 $ 4,717,850 $ 177,255 $ 698,762 Financial Solutions operations 24,349 631,097 333,107 133,501 90,458 Canada operations: Traditional operations 928,642 178,927 707,428 10,621 265,250 Financial Solutions operations 38,701 2,692 36,275 — 2,718 Europe, Middle East and Africa operations: Traditional operations 1,140,062 50,301 999,005 33,795 132,290 Financial Solutions operations 180,271 125,282 178,014 — 24,497 Asia Pacific operations: Traditional operations 1,681,505 83,049 1,345,951 24,597 286,674 Financial Solutions operations 5,428 23,648 37,976 1,423 19,920 Corporate and Other 342 117,057 2,460 — 217,738 Total $ 9,248,871 $ 1,911,886 $ 8,358,066 $ 381,192 $ 1,738,307 2015 U.S. and Latin America operations: Traditional operations $ 4,806,706 $ 636,779 $ 4,444,196 $ 131,439 $ 653,620 Financial Solutions operations 22,177 566,180 310,464 40,416 85,022 Canada operations: Traditional operations 838,894 182,621 670,477 11,299 217,061 Financial Solutions operations 37,969 1,436 29,251 — 1,881 Europe, Middle East and Africa operations: Traditional operations 1,121,540 51,370 979,225 39,164 123,943 Financial Solutions operations 171,830 73,432 161,917 — 16,304 Asia Pacific operations: Traditional operations 1,551,586 80,549 1,208,984 7,373 316,346 Financial Solutions operations 19,474 18,678 20,766 185 16,011 Corporate and Other 565 123,450 1,066 — 186,973 Total $ 8,570,741 $ 1,734,495 $ 7,826,346 $ 229,876 $ 1,617,161

Supplemental Schedule of Rein55

Supplemental Schedule of Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Supplemental Schedule Of Reinsurance Premiums For Insurance Companies [Table Text Block]	REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE IV—REINSURANCE (in millions) As of or for the Year ended December 31, Gross Amount Ceded to Other Companies Assumed from Other Companies Net Amounts Percentage of Amount Assumed to Net 2017 Life insurance in force $ 1,462 $ 205,529 $ 3,297,275 $ 3,093,208 106.6 % Premiums U.S. and Latin America operations: Traditional operations $ 30.5 $ 610.4 $ 5,936.2 $ 5,356.3 110.8 % Financial Solutions operations 4.3 — 19.4 23.7 81.9 Canada operations: Traditional operations — 38.1 940.1 902.0 104.2 Financial Solutions operations — — 38.2 38.2 100.0 Europe, Middle East and Africa operations: Traditional operations 26.6 34.9 1,310.0 1,301.7 100.6 Financial Solutions operations 0.2 125.0 288.5 163.7 176.2 Asia Pacific operations: Traditional operations — 54.5 2,107.5 2,053.0 102.7 Financial Solutions operations — — 2.4 2.4 100.0 Corporate and Other — — 0.1 0.1 100.0 Total $ 61.6 $ 862.9 $ 10,642.4 $ 9,841.1 108.1 2016 Life insurance in force $ 1,576 $ 214,727 $ 3,062,525 $ 2,849,374 107.5 % Premiums U.S. and Latin America operations: Traditional operations $ 31.6 $ 616.0 $ 5,834.0 $ 5,249.6 111.1 % Financial Solutions operations 1.6 40.2 63.0 24.4 258.2 Canada operations: Traditional operations — 36.5 965.1 928.6 103.9 Financial Solutions operations — — 38.7 38.7 100.0 Europe, Middle East and Africa operations: Traditional operations 24.1 30.9 1,146.9 1,140.1 100.6 Financial Solutions operations 0.3 84.4 264.4 180.3 146.6 Asia Pacific operations: Traditional operations — 50.3 1,731.8 1,681.5 103.0 Financial Solutions operations — — 5.4 5.4 100.0 Corporate and Other — — 0.3 0.3 100.0 Total $ 57.6 $ 858.3 $ 10,049.6 $ 9,248.9 108.7 2015 Life insurance in force $ 1,686 $ 222,388 $ 2,995,079 $ 2,774,377 108.0 % Premiums U.S. and Latin America operations: Traditional operations $ 29.4 $ 607.0 $ 5,384.3 $ 4,806.7 112.0 % Financial Solutions operations 2.9 38.8 58.1 22.2 261.7 Canada operations: Traditional operations — 42.3 881.2 838.9 105.0 Financial Solutions operations — — 38.0 38.0 100.0 Europe, Middle East and Africa operations: Traditional operations 10.7 25.5 1,136.3 1,121.5 101.3 Financial Solutions operations 0.1 89.1 260.8 171.8 151.8 Asia Pacific operations: Traditional operations — 41.0 1,592.6 1,551.6 102.6 Financial Solutions operations — — 19.5 19.5 100.0 Corporate and Other — — 0.5 0.5 100.0 Total $ 43.1 $ 843.7 $ 9,371.3 $ 8,570.7 109.3

Valuation and Qualifying Acco56

Valuation and Qualifying Accounts (Tables)	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Valuation And Qualifying Accounts [Table Text Block]	REINSURANCE GROUP OF AMERICA, INCORPORATED SCHEDULE V—VALUATION AND QUALIFYING ACCOUNTS (in millions) Additions Description Balance at Beginning of Period Charged to Costs and Expenses Charged to Other Accounts Deductions Balance at End of Period 2017 Valuation allowance for deferred income taxes $ 133.4 $ 88.5 $ 10.6 $ 5.6 $ 226.9 Valuation allowance for mortgage loans 7.7 1.7 — — 9.4 2016 Valuation allowance for deferred income taxes $ 127.1 $ 11.0 $ (4.7 ) $ — $ 133.4 Valuation allowance for mortgage loans 6.8 0.9 — — 7.7 2015 Valuation allowance for deferred income taxes $ 112.0 $ 23.7 $ (8.6 ) $ — $ 127.1 Valuation allowance for mortgage loans 6.5 0.3 — — 6.8

Summary of Significant Accoun57

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Collateral Obtained Percent Of Fair Value Reverse Repurchase Agreements	100.00%
Property, Plant and Equipment, Useful Life	40 years
Other Asset Impairment Charges	$ 24.5	$ 0.6	$ 6
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	79.4	60.8
Property, Plant and Equipment, Gross	236.1	221.7
Depreciation	17.2	16.6	17.1
Capital Leased Assets, Gross	136.3	145.7
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	30.5	21
Amortization of Leased Asset	9.4	9.6	10
Goodwill	7	7
Present Value of Future Insurance Profits, Net	3.3	3.1
Accumulated Amortization Of Value Of Business Acquired VOBA	14.6	14.3
Amortization of Value of Business Acquired (VOBA)	0.3	0.5	0.4
Values Of Business Acquired Distribution Agreements And Customer Relationships	52.3	61.2
Accumulated Amortization Of Values Of Business Acquired Distribution Agreements And Customer Relationships	72.1	63.2
Amortization Of Values Of Business Acquired Distribution Agreements And Customer Relationships	8.9	9.3	9.5
Future Amortization Expense, Year One	8.6
Future Amortization Expense, Year Two	8.3
Future Amortization Expense, Year Three	7.8
Future Amortization Expense, Year Four	6.9
Future Amortization Expense, Year Five	6.6
Capitalized Computer Software, Net	145.5	139.8
Capitalized Computer Software, Amortization	$ 35.7	$ 10.3	$ 14
Value of Customer Relationships Acquired [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Value of Distribution Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years

Summary of Significant Accoun58

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Future Policy Benefits) (Narrative) (Details)	Dec. 31, 2017
Maximum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	6.00%
Minimum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	3.00%

Summary of Significant Accoun59

Summary of Significant Accounting Policies (New Accounting Pronouncements) (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle	$ 17,700
Effective Income Tax Rate Reconciliation, Equity in Earnings (Losses) of Unconsolidated Subsidiary, Amount	10,532	$ 0	$ 0
Contractual Obligation	38,200
Accounting Standards Update 2018 02 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	17,723
AOCI Attributable to Parent [Member] | Accounting Standards Update 2018 02 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 156,372

Acquisitions (Narrative) (Detai

Acquisitions (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015
Business Combinations [Abstract]
Business Acquisition, Name of Acquired Entity	PGGM Levensverzekeringen, N.V.	Aurora National
Business Acquisition, Percentage of Voting Interests Acquired		100.00%
Payments to Acquire Businesses, Gross		$ 191.5
Noncash or Part Noncash Acquisition, Value of Assets Acquired	$ 404.4	3,700
Noncash or Part Noncash Acquisition, Investments Acquired	395.6	3,600
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed	$ 394.1	$ 3,500

Investments (Investments in Fix

Investments (Investments in Fixed Maturity and Equity Securities Available-for-Sale by Sector) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 21,966,803	$ 18,924,711
Available-for-sale Securities	23,210,968	19,619,084
Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	35,281,412	30,211,787
Available-for-sale Securities, Gross Unrealized Gains	2,982,754	2,243,037
Available-for-sale Securities, Gross Unrealized Losses	113,346	361,199
Available-for-sale Securities	$ 38,150,820	$ 32,093,625
Percentage Of Total Available For Sale Securities	100.00%	100.00%
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	$ 275	$ 100
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	102,841	285,579
Available-for-sale Securities, Gross Unrealized Gains	958	3,440
Available-for-sale Securities, Gross Unrealized Losses	3,647	13,658
Available-for-sale Securities	$ 100,152	$ 275,361
Percentage Of Total Available For Sale Securities	100.00%	100.00%
Corporate Debt Securities [Member] | Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 21,966,803	$ 18,924,711
Available-for-sale Securities, Gross Unrealized Gains	1,299,594	911,618
Available-for-sale Securities, Gross Unrealized Losses	55,429	217,245
Available-for-sale Securities	$ 23,210,968	$ 19,619,084
Percentage Of Total Available For Sale Securities	60.90%	61.10%
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	$ 0	$ 0
Canadian Provincial Governments [Member] | Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	2,843,273	2,561,605
Available-for-sale Securities, Gross Unrealized Gains	1,378,510	1,085,982
Available-for-sale Securities, Gross Unrealized Losses	1,707	3,541
Available-for-sale Securities	$ 4,220,076	$ 3,644,046
Percentage Of Total Available For Sale Securities	11.10%	11.40%
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	$ 0	$ 0
Residential Mortgage Backed Securities [Member] | Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,695,126	1,258,039
Available-for-sale Securities, Gross Unrealized Gains	36,632	33,917
Available-for-sale Securities, Gross Unrealized Losses	11,878	13,380
Available-for-sale Securities	$ 1,719,880	$ 1,278,576
Percentage Of Total Available For Sale Securities	4.50%	4.00%
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	$ 0	$ 375
Asset-backed Securities [Member] | Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,634,758	1,443,822
Available-for-sale Securities, Gross Unrealized Gains	18,798	9,350
Available-for-sale Securities, Gross Unrealized Losses	5,194	23,828
Available-for-sale Securities	$ 1,648,362	$ 1,429,344
Percentage Of Total Available For Sale Securities	4.30%	4.50%
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	$ 275	$ 275
Commercial Mortgage Backed Securities [Member] | Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,285,594	1,342,440
Available-for-sale Securities, Gross Unrealized Gains	22,627	28,973
Available-for-sale Securities, Gross Unrealized Losses	4,834	7,759
Available-for-sale Securities	$ 1,303,387	$ 1,363,654
Percentage Of Total Available For Sale Securities	3.40%	4.20%
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	$ 0	$ 0
US Treasury and Government [Member] | Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,953,436	1,518,702
Available-for-sale Securities, Gross Unrealized Gains	12,089	12,644
Available-for-sale Securities, Gross Unrealized Losses	21,933	63,044
Available-for-sale Securities	$ 1,943,592	$ 1,468,302
Percentage Of Total Available For Sale Securities	5.10%	4.60%
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	$ 0	$ 0
US States and Political Subdivisions Debt Securities [Member] | Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	647,727	566,761
Available-for-sale Securities, Gross Unrealized Gains	59,997	37,499
Available-for-sale Securities, Gross Unrealized Losses	4,296	12,464
Available-for-sale Securities	$ 703,428	$ 591,796
Percentage Of Total Available For Sale Securities	1.80%	1.80%
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	$ 0	$ 0
Foreign Government Debt Securities [Member] | Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	3,254,695	2,595,707
Available-for-sale Securities, Gross Unrealized Gains	154,507	123,054
Available-for-sale Securities, Gross Unrealized Losses	8,075	19,938
Available-for-sale Securities	$ 3,401,127	$ 2,698,823
Percentage Of Total Available For Sale Securities	8.90%	8.40%
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	$ 0	$ 0
Nonredeemable Preferred Stock [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	41,553	55,812
Available-for-sale Securities, Gross Unrealized Gains	479	1,648
Available-for-sale Securities, Gross Unrealized Losses	2,226	6,337
Available-for-sale Securities	$ 39,806	$ 51,123
Percentage Of Total Available For Sale Securities	39.70%	18.60%
Equity Securities Other Than Non-redeemable Preferred Stock [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 61,288	$ 229,767
Available-for-sale Securities, Gross Unrealized Gains	479	1,792
Available-for-sale Securities, Gross Unrealized Losses	1,421	7,321
Available-for-sale Securities	$ 60,346	$ 224,238
Percentage Of Total Available For Sale Securities	60.30%	81.40%

Investments (Fixed Maturity Sec

Investments (Fixed Maturity Securities Pledged And Received As Collateral) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 21,966,803	$ 18,924,711
Available-for-sale Securities	23,210,968	19,619,084
Assets Held-in-trust	841,500	893,800
Reported Value Measurement [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held-in-trust	15,584,296	12,135,258
Reported Value Measurement [Member] | Securities Pledged as Collateral [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	72,542	207,066
Estimate of Fair Value Measurement [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held-in-trust	16,715,281	12,874,370
Estimate of Fair Value Measurement [Member] | Securities Pledged as Collateral [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	75,622	210,676
Estimate of Fair Value Measurement [Member] | Collateral Received Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 590,417	$ 300,925

Investments (Exposure To Concen

Investments (Exposure To Concentrations Of Credit Risk) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 21,966,803	$ 18,924,711
Available-for-sale Securities	23,210,968	19,619,084
Canadian Province Of Ontario Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,119,337	1,004,261
Available-for-sale Securities	1,917,996	1,612,957
Canadian Province Of Quebec Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	939,837	832,764
Available-for-sale Securities	$ 1,282,944	$ 1,126,433

Investments (Amortized Cost and

Investments (Amortized Cost and Fair Value of Fixed Maturities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Available-for-sale Securities, Debt Maturities, within One Year, Amortized Cost Basis	$ 864,993
Available-for-sale Securities, Debt Maturities, after One Through Five Years, Amortized Cost Basis	7,988,167
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	9,286,543
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	12,526,231
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis	4,615,478
Available for Sale at Fair value - Amortized cost	35,281,412	$ 30,211,787
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Available-for-sale Securities, Debt Maturities, within One Year, Fair Value	868,802
Available-for-sale Securities, Debt Maturities, after One Through Five Years, Fair Value	8,234,097
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Fair Value	9,781,323
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	14,594,969
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value	4,671,629
Fixed maturity securities available-for-sale	$ 38,150,820	$ 32,093,625

Investments (Amortized Cost a65

Investments (Amortized Cost and Fair Value of Fixed Maturity Holdings by Industry Type) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Corporate Secturities by Investment Sector And Credit Rating [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 21,966,803	$ 18,924,711
Available-for-sale Securities	$ 23,210,968	$ 19,619,084
Percentage Of Total Available For Sales Securities	100.00%	100.00%
Financial Services Sector [Member]
Corporate Secturities by Investment Sector And Credit Rating [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 7,977,885	$ 6,725,199
Available-for-sale Securities	$ 8,362,774	$ 6,888,968
Percentage Of Total Available For Sales Securities	36.10%	35.20%
Commercial and Industrial Sector [Member]
Corporate Secturities by Investment Sector And Credit Rating [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 11,535,166	$ 10,228,813
Available-for-sale Securities	$ 12,199,333	$ 10,639,613
Percentage Of Total Available For Sales Securities	52.50%	54.20%
Utility Industry [Member]
Corporate Secturities by Investment Sector And Credit Rating [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 2,453,752	$ 1,970,699
Available-for-sale Securities	$ 2,648,861	$ 2,090,503
Percentage Of Total Available For Sales Securities	11.40%	10.60%

Investments (Credit Losses Reco

Investments (Credit Losses Recognized in Earnings on Fixed Maturity Securities Held by the Company) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance, beginning of period	$ 6,013	$ 7,284	$ 7,284
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	0	231	0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Change in Status	(2,336)	0	0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold	0	(1,502)	0
Balance, end of period	$ 3,677	$ 6,013	$ 7,284

Investments (Fair Value Below A

Investments (Fair Value Below Amortized Cost of Gross Unrealized Losses for Fixed Maturity and Equity Securities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Gross unrealized losses with number of securities [Line Items]
Available-for-sale Securities, Gross Unrealized Losses	$ 116,993	$ 374,857
Percentage Of Total Gross Unrealized Losses	100.00%	100.00%
Less Than 20 Percent [Member]
Gross unrealized losses with number of securities [Line Items]
Available-for-sale Securities, Gross Unrealized Losses	$ 113,466	$ 337,831
Percentage Of Total Gross Unrealized Losses	97.00%	90.10%
More Than Or Equal To 20 Percent For Less Than Six Months [Member]
Gross unrealized losses with number of securities [Line Items]
Available-for-sale Securities, Gross Unrealized Losses	$ 689	$ 19,438
Percentage Of Total Gross Unrealized Losses	0.60%	5.20%
More Than Or Equal To 20 Percent For Six Months Or Greater [Member]
Gross unrealized losses with number of securities [Line Items]
Available-for-sale Securities, Gross Unrealized Losses	$ 2,838	$ 17,588
Percentage Of Total Gross Unrealized Losses	2.40%	4.70%

Investments (Fair Value and Los

Investments (Fair Value and Losses by Investment Category and Length of Time in a Loss Position) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 4,565,273	$ 8,327,843
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	40,239	253,005
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,738,393	1,210,148
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	73,107	108,194
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	7,303,666	9,537,991
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	113,346	361,199
Fixed Maturities [Member] | External Credit Rating, Investment Grade [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	4,339,799	7,953,012
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	36,789	242,398
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,644,670	994,240
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	65,548	62,785
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	6,984,469	8,947,252
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	102,337	305,183
Fixed Maturities [Member] | External Credit Rating, Investment Grade [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,886,212	4,661,706
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	17,099	124,444
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,009,750	549,273
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	28,080	43,282
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,895,962	5,210,979
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	45,179	167,726
Fixed Maturities [Member] | External Credit Rating, Investment Grade [Member] | Canadian Provincial Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	18,688	101,578
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	91	3,541
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	111,560	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	1,596	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	130,248	101,578
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	1,687	3,541
Fixed Maturities [Member] | External Credit Rating, Investment Grade [Member] | Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	566,699	490,473
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	5,852	9,733
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	224,439	112,216
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	6,004	3,635
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	791,138	602,689
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	11,856	13,368
Fixed Maturities [Member] | External Credit Rating, Investment Grade [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	434,274	563,259
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	2,707	12,010
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	168,524	257,166
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	2,434	9,653
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	602,798	820,425
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	5,141	21,663
Fixed Maturities [Member] | External Credit Rating, Investment Grade [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	220,401	368,465
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	1,914	6,858
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	103,269	10,853
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	2,920	166
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	323,670	379,318
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	4,834	7,024
Fixed Maturities [Member] | External Credit Rating, Investment Grade [Member] | US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	800,298	1,056,101
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	6,177	63,044
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	767,197	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	15,756	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,567,495	1,056,101
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	21,933	63,044
Fixed Maturities [Member] | External Credit Rating, Investment Grade [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	43,510	187,194
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	242	9,396
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	68,666	13,635
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	4,054	3,068
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	112,176	200,829
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	4,296	12,464
Fixed Maturities [Member] | External Credit Rating, Investment Grade [Member] | Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	369,717	524,236
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	2,707	13,372
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	191,265	51,097
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	4,704	2,981
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	560,982	575,333
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	7,411	16,353
Fixed Maturities [Member] | External Credit Rating, Non Investment Grade [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	225,474	374,831
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	3,450	10,607
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	93,723	215,908
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	7,559	45,409
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	319,197	590,739
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	11,009	56,016
Fixed Maturities [Member] | External Credit Rating, Non Investment Grade [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	194,879	330,757
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	3,317	7,914
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	75,731	163,152
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	6,933	41,605
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	270,610	493,909
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	10,250	49,519
Fixed Maturities [Member] | External Credit Rating, Non Investment Grade [Member] | Canadian Provincial Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,995
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	20
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,995
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	20
Fixed Maturities [Member] | External Credit Rating, Non Investment Grade [Member] | Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,369	412
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	22	12
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,369	412
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	22	12
Fixed Maturities [Member] | External Credit Rating, Non Investment Grade [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	5,904
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0	700
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,489	12,581
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	53	1,465
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,489	18,485
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	53	2,165
Fixed Maturities [Member] | External Credit Rating, Non Investment Grade [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		5,815
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		735
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		5,815
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		735
Fixed Maturities [Member] | External Credit Rating, Non Investment Grade [Member] | Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	28,600	32,355
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	113	1,258
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	15,134	39,763
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	551	2,327
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	43,734	72,118
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	664	3,585
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	5,902	212,899
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	1,024	7,851
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	73,722	28,630
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	2,623	5,807
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	79,624	241,529
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	3,647	13,658
Equity Securities [Member] | Nonredeemable Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	82	10,831
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	1	831
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	26,471	21,879
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	2,225	5,506
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	26,553	32,710
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	2,226	6,337
Equity Securities [Member] | Equity Securities Other Than Non-redeemable Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	5,820	202,068
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	1,023	7,020
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	47,251	6,751
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	398	301
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	53,071	208,819
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$ 1,421	$ 7,321

Investments (Investment Income

Investments (Investment Income Net of Related Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	$ 2,235,362	$ 1,983,975	$ 1,802,539
Investment Income, Investment Expense	(80,711)	(72,089)	(68,044)
Investment income, net of related expenses	2,154,651	1,911,886	1,734,495
Available-for-sale Securities [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	1,401,585	1,285,406	1,177,706
Mortgage Loans on Real Estate [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	197,755	168,582	149,564
Policy Loans [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	60,617	63,837	62,955
Funds Withheld At Interest [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	457,774	368,728	343,031
Short-term Investments [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	7,171	8,051	7,574
Other Aggregated Investments [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	$ 110,460	$ 89,371	$ 61,709

Investments (Investment Related

Investments (Investment Related Gains (Losses) Net) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Available-for-sale Securities [Abstract]
Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount	$ 42,639	$ 38,805	$ 57,380
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	0	(74)	0
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net	42,639	38,731	57,380
Impairment Losses On Equity Securities	(1,202)	0	0
Available-for-sale Securities, Gross Realized Gains	110,569	154,370	73,079
Available-for-sale Securities, Gross Realized Losses	(41,679)	(49,965)	(71,893)
Other Impairment Losses And Change In Mortgage Loan Provision	(9,497)	(11,006)	(6,953)
Derivatives And Other Investments Net	152,328	39,527	(101,603)
Realized Investment Gains (Losses)	$ 167,880	$ 94,195	$ (164,750)

Investments (Borrowed Securitie

Investments (Borrowed Securities Repurchased Securities And Repurchased Reversed Repurchased Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Securities Received as Collateral	$ 128,000	$ 80,000
Securities for Reverse Repurchase Agreements	413,819	476,531
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities	417,550	515,200
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Cash	31,200	28,800
Estimate of Fair Value Measurement [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Borrowed	377,820	279,186
Securities Loaned, Fair Value of Collateral	121,551	73,625
Securities for Reverse Repurchase Agreements	428,344	499,891
Reported Value Measurement [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Borrowed	358,875	263,820
Securities Loaned, Fair Value of Collateral	$ 117,246	$ 74,389

Investments (Securities Pledged

Investments (Securities Pledged as Collateral Related to Repurchase Reverse Repurchase Program) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	$ 121,551	$ 73,625
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	428,344	499,891
Securities Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	576,786	624,032
Secured Borrowings, Gross, Difference, Amount	26,891	50,516
Obligation to Return Securities Received as Collateral	549,895	573,516
Maturity Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	0	0
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	1,131	1,246
Obligation to Return Securities Received as Collateral	1,131	1,246
Maturity Less than 30 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	0	0
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
Obligation to Return Securities Received as Collateral	0	0
Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	0	4,017
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	312	3,220
Obligation to Return Securities Received as Collateral	312	7,237
Maturity Greater than 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	121,551	69,608
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	426,901	495,425
Obligation to Return Securities Received as Collateral	548,452	565,033
Corporate Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	121,551	73,625
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	184,646	170,199
Corporate Debt Securities [Member] | Maturity Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	0	0
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
Corporate Debt Securities [Member] | Maturity Less than 30 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	0	0
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
Corporate Debt Securities [Member] | Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	0	4,017
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	312	3,220
Corporate Debt Securities [Member] | Maturity Greater than 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	121,551	69,608
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	184,334	166,979
Residential Mortgage Backed Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	92,546
Residential Mortgage Backed Securities [Member] | Maturity Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
Residential Mortgage Backed Securities [Member] | Maturity Less than 30 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
Residential Mortgage Backed Securities [Member] | Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
Residential Mortgage Backed Securities [Member] | Maturity Greater than 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	92,546
US Government Agencies Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	220,765	216,000
US Government Agencies Debt Securities [Member] | Maturity Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
US Government Agencies Debt Securities [Member] | Maturity Less than 30 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
US Government Agencies Debt Securities [Member] | Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
US Government Agencies Debt Securities [Member] | Maturity Greater than 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	220,765	216,000
Foreign Government Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	21,802	19,900
Foreign Government Debt Securities [Member] | Maturity Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
Foreign Government Debt Securities [Member] | Maturity Less than 30 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
Foreign Government Debt Securities [Member] | Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
Foreign Government Debt Securities [Member] | Maturity Greater than 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	21,802	19,900
Other Debt Obligations [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	1,131	1,246
Other Debt Obligations [Member] | Maturity Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	1,131	1,246
Other Debt Obligations [Member] | Maturity Less than 30 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
Other Debt Obligations [Member] | Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	0	0
Other Debt Obligations [Member] | Maturity Greater than 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	$ 0	$ 0

Investments (Mortgage Loans by

Investments (Mortgage Loans by Property Type) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 4,413,171	$ 3,783,207
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%	100.00%
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	$ (3,254)	$ 0
Allowance for Loan and Lease Losses, Real Estate	(9,384)	(7,685)	$ (6,813)	$ (6,471)
Mortgage loans on real estate	4,400,533	3,775,522
Office Building [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 1,487,392	$ 1,270,113
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	33.60%	33.60%
Retail Site [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 1,270,676	$ 1,179,936
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	28.80%	31.20%
Industrial Property [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 938,612	$ 713,461
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	21.30%	18.80%
Apartment Building [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 510,052	$ 447,088
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	11.60%	11.80%
Other Property [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 206,439	$ 172,609
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	4.70%	4.60%

Investments (Mortgage Loans b74

Investments (Mortgage Loans by Maturity Date) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 4,413,171	$ 3,783,207
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%	100.00%
Mortgage Loans On Real Estate Due One Year Through Five Years [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 1,091,066	$ 822,073
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	24.80%	21.70%
Mortgage Loans On Real Estate Due After Five Years [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 2,516,872	$ 2,099,559
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	57.00%	55.50%
Mortgage Loans On Real Estate Due After Ten Years [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 805,233	$ 861,575
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	18.20%	22.80%

Investments (Mortgage Loans b75

Investments (Mortgage Loans by Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 4,413,171	$ 3,783,207
Loans Receivable, Gross, Commercial, Construction	$ 9,686
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%	100.00%
Greater than 1.20x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 4,182,753	$ 3,601,817
1.00x - 1.20x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	151,281	120,296
Less than 1.00x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	69,451	61,094
0% - 59.99%
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	2,206,208	$ 1,925,755
Loans Receivable, Gross, Commercial, Construction	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	50.00%	50.80%
0% - 59.99% | Greater than 1.20x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 2,148,428	$ 1,859,640
0% - 59.99% | 1.00x - 1.20x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	53,979	64,749
0% - 59.99% | Less than 1.00x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	3,801	1,366
60% - 69.99%
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	1,608,078	$ 1,292,466
Loans Receivable, Gross, Commercial, Construction	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	36.40%	34.20%
60% - 69.99% | Greater than 1.20x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 1,517,029	$ 1,257,788
60% - 69.99% | 1.00x - 1.20x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	47,128	34,678
60% - 69.99% | Less than 1.00x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	43,921	0
70% - 79.99%
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	431,274	$ 415,330
Loans Receivable, Gross, Commercial, Construction	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	9.80%	11.00%
70% - 79.99% | Greater than 1.20x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 396,446	$ 370,092
70% - 79.99% | 1.00x - 1.20x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	19,461	20,869
70% - 79.99% | Less than 1.00x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	15,367	24,369
Greater than 80%
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	167,611	$ 149,656
Loans Receivable, Gross, Commercial, Construction	$ 9,686
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	3.80%	4.00%
Greater than 80% | Greater than 1.20x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 120,850	$ 114,297
Greater than 80% | 1.00x - 1.20x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	30,713	0
Greater than 80% | Less than 1.00x
Financing Receivable, Recorded Investment [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 6,362	$ 35,359

Investments (Mortgage Loans Age

Investments (Mortgage Loans Age Analysis) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 4,413,171	$ 3,783,207
Financing Receivable, Recorded Investment, Current	4,394,015	3,783,207
Financing Receivable, Recorded Investment, Past Due	19,156	0
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	17,100	0
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 2,056	$ 0

Investments (Mortgage Loans b77

Investments (Mortgage Loans by Method of Evaluation and Related Valuation Allowances) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Mortgage Loans [Abstract]
Financing Receivable, Individually Evaluated for Impairment	$ 5,858	$ 2,216
Financing Receivable, Collectively Evaluated for Impairment	4,407,313	3,780,991
Loans Receivable, Gross, Commercial, Real Estate	4,413,171	3,783,207
Valuation Allowances [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	9,384	7,685
Allowance for Loan and Lease Losses, Real Estate	$ 9,384	$ 7,685	$ 6,813	$ 6,471

Investments (Loan Valuation All

Investments (Loan Valuation Allowance for Mortgage Loans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Balance beginning	$ 7,685	$ 6,813	$ 6,471
Provision	1,691	872	342
Balance ending	9,384	7,685	6,813
Valuation Allowances and Reserves, Additions for Adjustments	$ 8	$ 0	$ 0

Investments (Impaired Mortgage

Investments (Impaired Mortgage Loans) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		$ 6,427	$ 2,758
Impaired Financing Receivable, Recorded Investment		5,858	2,216
Impaired Financing Receivable, Related Allowance		0	0
Impaired Financing Receivable Net Of Related Allowance		5,858	2,216
Impaired Financing Receivable, Average Recorded Investment	[1]	3,621	2,249		$ 17,625
Impaired Financing Receivable, Interest Income, Accrual Method		186	142		1,100
Impaired mortgage loans with no valuation allowance recorded
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		6,427	2,758
Impaired Financing Receivable, Recorded Investment		5,858	2,216
Impaired Financing Receivable, Related Allowance		0	0
Impaired Financing Receivable Net Of Related Allowance		5,858	2,216
Impaired Financing Receivable, Average Recorded Investment		3,621	2,249	[1]	6,033	[1]
Impaired Financing Receivable, Interest Income, Accrual Method		186	142		330
Impaired mortgage loans with valuation allowance recorded
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		0	0
Impaired Financing Receivable, Recorded Investment		0	0
Impaired Financing Receivable, Related Allowance		0	0
Impaired Financing Receivable Net Of Related Allowance		0	0
Impaired Financing Receivable, Average Recorded Investment		0	0	[1]	11,592	[1]
Impaired Financing Receivable, Interest Income, Accrual Method		$ 0	$ 0		$ 770
[1]	Average recorded investment represents the average loan balances as of the beginning of period and all subsequent quarterly end of period balances.

Investments (Other Invested Ass

Investments (Other Invested Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Investments [Abstract]
Other invested assets	$ 1,605,484	$ 1,591,940
Equity Securities [Member]
Other Investments [Abstract]
Other invested assets	100,152	275,361
Limited Partner [Member]
Other Investments [Abstract]
Other invested assets	781,124	687,522
Gain (Loss) on Derivatives [Member]
Other Investments [Abstract]
Other invested assets	137,613	229,108
Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Other Investments [Abstract]
Other invested assets	218,541	190,120
Other [Member]
Other Investments [Abstract]
Other invested assets	$ 368,054	$ 209,829

Investments Investments (Narrat

Investments Investments (Narrative) (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2017USD ($)position	Dec. 31, 2016USD ($)position	Dec. 31, 2015USD ($)
Investment Narrative [Line Items]
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Cash		$ 31,200	$ 28,800
Net Amount Assets Liabilities From Repurchase Reverse Repurchase Agreements		1,100	5,500
Available-for-sale Securities, Amortized Cost Basis		21,966,803	18,924,711
Available-for-sale Securities		$ 23,210,968	$ 19,619,084
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | position		1,116	1,535
Proceeds From Sale Of Available For Sale Securities Sold At Loss		$ 2,727,800	$ 1,181,600	$ 1,523,600
Available-for-sale Securities, Gross Realized Losses		41,679	49,965	$ 71,893
Securities for Reverse Repurchase Agreements		$ 413,819	$ 476,531
Mortgage Loan Percent Of Invested Assets		8.50%	8.40%
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due		$ 19,156	$ 0
Policy Loans Percent Of Invested Assets		2.60%	3.20%
Funds Withheld At Interest Percent Of Invested Assets		11.80%	13.10%
Percentage Of Total Gross Unrealized Losses		100.00%	100.00%
Funds withheld at interest		$ 6,083,388	$ 5,875,919
Funds Held Under Reinsurance Agreements Asset Specific Client		$ 4,100,000
Other Invested Assets Percent Of Invested Assets		3.10%	3.60%
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total		100.00%	100.00%
Collateral Obtained Percent Of Fair Value Reverse Repurchase Agreements		100.00%
Non-Income Producing Securities [Member]
Investment Narrative [Line Items]
Available-for-sale Securities, Amortized Cost Basis		$ 38,800	$ 35,400
Available-for-sale Securities		39,300	47,300
Canadian Province Of Quebec Securities [Member]
Investment Narrative [Line Items]
Available-for-sale Securities, Amortized Cost Basis		939,837	832,764
Available-for-sale Securities		1,282,944	1,126,433
Reported Value Measurement [Member]
Investment Narrative [Line Items]
Securities Borrowed		358,875	263,820
Funds withheld at interest	[1]	$ 5,955,092	$ 5,893,381
CALIFORNIA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total		19.50%
TEXAS
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total		8.40%
GEORGIA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total		7.60%
CANADA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total		2.30%
[1]	Carrying values presented herein may differ from those in the Company’s consolidated balance sheets because certain items within the respective financial statement captions may be measured at fair value on a recurring basis.

Derivative Instruments (Gross N

Derivative Instruments (Gross Notional Amount and Fair Value of Derivatives Contracts) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Notional Amount of Derivatives	$ 15,904,127	$ 14,012,598
Derivative Asset, Fair Value, Gross Asset	320,724	283,094
Derivative Liability, Fair Value, Gross Liability	1,058,727	1,061,408
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount of Derivatives	14,243,031	12,649,093
Derivative Asset, Fair Value, Gross Asset	254,252	150,834
Derivative Liability, Fair Value, Gross Liability	1,022,122	1,029,451
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount of Derivatives	996,204	949,556
Derivative Asset, Fair Value, Gross Asset	59,809	78,405
Derivative Liability, Fair Value, Gross Liability	2,372	5,949
Not Designated as Hedging Instrument [Member] | Future [Member]
Derivative [Line Items]
Notional Amount of Derivatives	412,438	475,968
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Derivative [Line Items]
Notional Amount of Derivatives	6,030	25,000
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	28	5,070
Not Designated as Hedging Instrument [Member] | Consumer Price Index Swap [Member]
Derivative [Line Items]
Notional Amount of Derivatives	221,932	20,615
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	2,160	262
Not Designated as Hedging Instrument [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Notional Amount of Derivatives	961,200	926,000
Derivative Asset, Fair Value, Gross Asset	8,319	12,012
Derivative Liability, Fair Value, Gross Liability	1,651	2,871
Not Designated as Hedging Instrument [Member] | Equity [Member]
Derivative [Line Items]
Notional Amount of Derivatives	632,251	525,894
Derivative Asset, Fair Value, Gross Asset	23,271	33,459
Derivative Liability, Fair Value, Gross Liability	0	0
Not Designated as Hedging Instrument [Member] | Longevity Swap [Member]
Derivative [Line Items]
Notional Amount of Derivatives	960,400	841,360
Derivative Asset, Fair Value, Gross Asset	40,659	26,958
Derivative Liability, Fair Value, Gross Liability	0	0
Not Designated as Hedging Instrument [Member] | Mortality Swap [Member]
Derivative [Line Items]
Notional Amount of Derivatives	0	50,000
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	1,683	2,462
Not Designated as Hedging Instrument [Member] | Synthetic Guaranteed Investment Contracts [Member]
Derivative [Line Items]
Notional Amount of Derivatives	10,052,576	8,834,700
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Not Designated as Hedging Instrument [Member] | Embedded Derivatives In Modified Coinsurance Or Funds Withheld Arrangements [Member]
Derivative [Line Items]
Notional Amount of Derivatives	0	0
Derivative Asset, Fair Value, Gross Asset	122,194	0
Derivative Liability, Fair Value, Gross Liability	0	22,529
Not Designated as Hedging Instrument [Member] | Embedded Derivatives In Indexed Annuity [Member]
Derivative [Line Items]
Notional Amount of Derivatives	0	0
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	861,758	805,672
Not Designated as Hedging Instrument [Member] | Embedded Derivatives In Variable Annuity [Member]
Derivative [Line Items]
Notional Amount of Derivatives	0	0
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	152,470	184,636
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount of Derivatives	1,661,096	1,363,505
Derivative Asset, Fair Value, Gross Asset	66,472	132,260
Derivative Liability, Fair Value, Gross Liability	36,605	31,957
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount of Derivatives	435,000	435,000
Derivative Asset, Fair Value, Gross Asset	0	27,901
Derivative Liability, Fair Value, Gross Liability	20,389	31,223
Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Derivative [Line Items]
Notional Amount of Derivatives	553,175	0
Derivative Asset, Fair Value, Gross Asset	1,265	0
Derivative Liability, Fair Value, Gross Liability	7,720	0
Designated as Hedging Instrument [Member] | Currency Swap [Member]
Derivative [Line Items]
Notional Amount of Derivatives	672,921	928,505
Derivative Asset, Fair Value, Gross Asset	65,207	104,359
Derivative Liability, Fair Value, Gross Liability	$ 8,496	$ 734

Derivative Instruments (Derivat

Derivative Instruments (Derivative Instruments Offsetting Balance Sheet) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Derivative Asset [Abstract]
Derivative Fair Value Of Free Standing Derivative Asset		$ 198,530	$ 283,094
Derivative Asset, Fair Value, Gross Liability		(20,258)	(27,028)
Derivative Asset		178,272	256,066
Derivative Asset, Fair Value of Collateral	[1],[2]	(862)	(16,913)
Derivative, Collateral, Obligation to Return Cash	[3]	(185,900)	(254,498)
Derivative Asset, Fair Value, Amount Offset Against Collateral		(8,490)	(15,345)
Derivative Liability [Abstract]
Derivative Fair Value Of Free Standing Derivative Liability		44,499	48,571
Derivative Liability, Fair Value, Gross Asset		(20,258)	(27,028)
Derivative Liability		24,241	21,543
Derivative Liability, Fair Value of Collateral	[2],[4]	(58,156)	(95,863)
Derivative, Collateral, Right to Reclaim Cash	[5]	(22,221)	(1,441)
Derivative Liability, Fair Value, Amount Offset Against Collateral		$ (56,136)	$ (75,761)
[1]	Consists of U.S. Treasury and government agency securities.
[2]	Includes initial margin posted to a central clearing partner.
[3]	Included in cash and cash equivalents, with obligation to return cash collateral recorded in other liabilities.
[4]	Included in available-for-sale securities, primarily consists of U.S. Treasury and government agency securities.
[5]	Consists of receivable from counterparty, included in other assets.

Derivative Instruments Derivati

Derivative Instruments Derivative Instruments (Fair Value Hedge Attributable to Foreign Currency) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	$ 9,456	$ (1,700)	$ 4,008
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	(9,456)	1,700	(4,008)
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net	$ 0	$ 0	$ 0

Derivative Instruments (Current

Derivative Instruments (Current Period Cash Flow Hedges in AOCI (loss) before Taxes) (Details) - Cash Flow Hedging [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Balance, Beginning of Period	$ (2,496)	$ (29,397)	$ (31,591)
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	6,316	27,110	2,676
Balance, End of Period	2,619	(2,496)	(29,397)
Gain (Loss) on Investments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(775)	278	87
Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(505)	(487)	(569)
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 79	$ 0	$ 0

Derivative Instruments (Cash Fl

Derivative Instruments (Cash Flow Hedges) (Details) - Cash Flow Hedging [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ 6,316	$ 27,110	$ 2,676
Gain (Loss) on Investments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	775	(278)	(87)
Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	505	487	569
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(79)	0	0
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(5,649)	27,901	(11,422)
Interest Rate Swap [Member] | Gain (Loss) on Investments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	0
Interest Rate Swap [Member] | Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	343
Interest Rate Swap [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(79)	0	0
Currency Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	11,955	(791)
Currency Swap [Member] | Gain (Loss) on Investments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0
Currency Swap [Member] | Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	380	510
Currency Swap [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0
Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	10	0	14,098
Forward Contracts [Member] | Gain (Loss) on Investments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	775	(278)	(87)
Forward Contracts [Member] | Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	125	(23)	226
Forward Contracts [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 0	$ 0	$ 0

Derivative Instruments (Hedges

Derivative Instruments (Hedges of Net Investments in Foreign Operations) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Gains Losses Deferred In Accumulated Other Comprehensive Income Loss On Derivatives	[1],[2]	$ (37,567)	$ (10,234)	$ 96,019
Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Gains Losses Deferred In Accumulated Other Comprehensive Income Loss On Derivatives	[1],[2]	$ (10,386)	$ 0	$ 0
[1]	There was no ineffectiveness recognized for the Company’s hedges of net investments in foreign operations.
[2]	There were no sales or substantial liquidations of net investments in foreign operations that would have required the reclassification of gains or losses from accumulated other comprehensive income (loss) into investment income during the periods presented.

Derivative Instruments (Non Hed

Derivative Instruments (Non Hedging Derivatives and Embedded Derivatives Effect on Income Statement) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ 167,880	$ 94,195	$ (164,750)
Other revenues	(352,108)	(266,559)	(277,692)
Gain Loss On Investments Related To Change In Fair Value Of Derivatives Excluding Embedded Derivatives	(42,767)	(28,611)	7,408
Interest credited	502,040	364,691	336,964
Not Designated as Hedging Instrument [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	54,060	44,101	(105,136)
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	11,278	7,649	20,358
Not Designated as Hedging Instrument [Member] | Interest Rate Options [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	0	0	3,275
Not Designated as Hedging Instrument [Member] | Future [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(36,160)	(40,242)	319
Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	591	1,630	(1,160)
Not Designated as Hedging Instrument [Member] | Consumer Price Index Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(2,078)	(401)	(208)
Not Designated as Hedging Instrument [Member] | Credit Default Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	18,118	18,100	(4,683)
Not Designated as Hedging Instrument [Member] | Equity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(42,953)	(28,270)	(16,899)
Not Designated as Hedging Instrument [Member] | Longevity Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Other revenues	(9,358)	(13,095)	(8,228)
Not Designated as Hedging Instrument [Member] | Mortality Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Other revenues	(921)	(172)	(1,822)
Not Designated as Hedging Instrument [Member] | Embedded Derivatives In Modified Coinsurance Or Funds Withheld Arrangements [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	144,723	54,169	(98,792)
Not Designated as Hedging Instrument [Member] | Embedded Derivatives In Indexed Annuity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Interest credited	(80,062)	10,708	19,440
Not Designated as Hedging Instrument [Member] | Embedded Derivatives In Variable Annuity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ 32,166	$ 7,835	$ (33,192)

Derivative Instruments (Exposur

Derivative Instruments (Exposure from Credit Derivatives by Rating of the Underlying Credits) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Credit Derivatives [Line Items]
Credit Risk Derivatives, at Fair Value, Net	[1]	$ 7,572	$ 8,970
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 951,300	$ 922,700
Derivative Average Remaining Maturity	[1],[3]	3 years 5 months	4 years 3 months
Standard Poors AAA To A Ratings [Member]
Credit Derivatives [Line Items]
Credit Risk Derivatives, at Fair Value, Net	[1]	$ 3,128	$ 1,726
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 162,000	$ 150,500
Derivative Average Remaining Maturity	[1],[3]	2 years 11 months	3 years 10 months
Standard & Poor's, BBB Rating [Member]
Credit Derivatives [Line Items]
Credit Risk Derivatives, at Fair Value, Net	[1]	$ 4,414	$ 7,721
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 784,300	$ 763,200
Derivative Average Remaining Maturity	[1],[3]	3 years 6 months	4 years 5 months
Standard & Poor's, BB+ Rating [Member]
Credit Derivatives [Line Items]
Credit Risk Derivatives, at Fair Value, Net	[1]	$ 30	$ (477)
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 5,000	$ 9,000
Derivative Average Remaining Maturity	[1],[3]	1 year 6 months	3 years 6 months
Single Name Credit Default Swaps [Member] | Standard Poors AAA To A Ratings [Member]
Credit Derivatives [Line Items]
Credit Risk Derivatives, at Fair Value, Net	[1]	$ 3,128	$ 1,726
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 162,000	$ 150,500
Derivative Average Remaining Maturity	[1],[3]	2 years 11 months	3 years 10 months
Single Name Credit Default Swaps [Member] | Standard & Poor's, BBB Rating [Member]
Credit Derivatives [Line Items]
Credit Risk Derivatives, at Fair Value, Net	[1]	$ 4,469	$ 1,426
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 361,700	$ 347,200
Derivative Average Remaining Maturity	[1],[3]	2 years 11 months	3 years 8 months
Single Name Credit Default Swaps [Member] | Standard & Poor's, BB+ Rating [Member]
Credit Derivatives [Line Items]
Credit Risk Derivatives, at Fair Value, Net	[1]	$ 30	$ (477)
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 5,000	$ 9,000
Derivative Average Remaining Maturity	[1],[3]	1 year 6 months	3 years 6 months
Credit Default Swaps Referencing Indices [Member] | Standard & Poor's, BBB Rating [Member]
Credit Derivatives [Line Items]
Credit Risk Derivatives, at Fair Value, Net	[1]	$ (55)	$ 6,295
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 422,600	$ 416,000
Derivative Average Remaining Maturity	[1],[3]	4 years	5 years
[1]	The rating agency designations are based on ratings from Standard and Poor’s (“S&P”).
[2]	Assumes the value of the referenced credit obligations is zero.
[3]	The weighted average years to maturity of the credit default swaps is calculated based on weighted average notional amounts.

Derivative Instruments (Changes

Derivative Instruments (Changes in Estimated Fair Value Related to Embedded Derivatives) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Embedded Derivatives In Modified Coinsurance Or Funds Withheld Arrangements And Variable Annuity Contracts [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ 144,723	$ 54,169	$ 98,792
Derivative, Gain (Loss) on Derivative, Net	48,316	9,160	(26,025)
Embedded Derivatives In Variable Annuity Contracts [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	32,166	7,835	(33,192)
Derivative, Gain (Loss) on Derivative, Net	53,645	(41,201)	(29,008)
Embedded Derivatives In Equity Indexed Annuities [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(80,062)	10,708	19,440
Derivative, Gain (Loss) on Derivative, Net	$ (68,808)	$ (4,148)	$ 6,204

Derivative Instruments (Credit

Derivative Instruments (Credit Exposure of Derivative Contracts) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Credit Exposure of Derivative Contracts [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net		$ 155,714	$ 236,985
Derivative, Collateral, Right to Reclaim Cash	[1]	22,221	1,441
Derivative Liability, Fair Value of Collateral	[2],[3]	58,156	95,863
Derivative, Collateral, Obligation to Return Cash	[4]	(185,900)	(254,498)
Derivative Asset, Fair Value of Collateral	[3],[5]	(862)	(16,913)
Deposits with Clearing Organizations and Others, Securities		(58,156)	(73,571)
Net Credit Exposure On Derivative Contracts		(8,827)	(10,693)
Margin Deposit Assets	[6]	$ 6,538	$ 9,687
[1]	Consists of receivable from counterparty, included in other assets.
[2]	Included in available-for-sale securities, primarily consists of U.S. Treasury and government agency securities.
[3]	Includes initial margin posted to a central clearing partner.
[4]	Included in cash and cash equivalents, with obligation to return cash collateral recorded in other liabilities.
[5]	Consists of U.S. Treasury and government agency securities.
[6]	Included in other assets.

Derivative Instruments (Narrati

Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Cumulative Foreign Currency Translation Gain Loss Recorded In Accumulated Other Comprehensive Income Loss For Net Investment In Foreign Operations Hedges	$ 113.7	$ 161.6
Derivative Instruments, Gain Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing	2	$ 0.4	$ 0.8
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	(0.8)
Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	$ 0.7

Fair Value of Assets and Liab93

Fair Value of Assets and Liabilities (Balances of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	$ 38,150,820	$ 32,093,625
Fair Value Measured On Recurring Basis Funds Held Under Reinsurance Agreements Asset Embedded Derivatives	122,194	(22,529)
Cash and Cash Equivalents, Fair Value Disclosure	356,788	338,601
Fair Value Measured On Recurring Basis Short Term Investments	50,746	44,241
Other Assets, Fair Value Disclosure	40,659	26,958
Investments, Fair Value Disclosure	456,306	705,625
Total	39,177,513	33,186,521
Liabilities, Fair Value Disclosure [Abstract]
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	1,014,228	990,308
Other Liabilities, Fair Value Disclosure		(1,011,851)
Total	1,038,469
Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	1,818,006	1,933,479
Fair Value Measured On Recurring Basis Funds Held Under Reinsurance Agreements Asset Embedded Derivatives	0	0
Cash and Cash Equivalents, Fair Value Disclosure	354,071	338,601
Fair Value Measured On Recurring Basis Short Term Investments	0	8,276
Other Assets, Fair Value Disclosure	0	0
Investments, Fair Value Disclosure	317,770	462,482
Total	2,489,847	2,742,838
Liabilities, Fair Value Disclosure [Abstract]
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	0	0
Other Liabilities, Fair Value Disclosure		0
Total	0
Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	34,098,204	27,932,189
Fair Value Measured On Recurring Basis Funds Held Under Reinsurance Agreements Asset Embedded Derivatives	0	0
Cash and Cash Equivalents, Fair Value Disclosure	2,717	0
Fair Value Measured On Recurring Basis Short Term Investments	47,650	32,619
Other Assets, Fair Value Disclosure	0	0
Investments, Fair Value Disclosure	138,536	243,143
Total	34,287,107	28,207,951
Liabilities, Fair Value Disclosure [Abstract]
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	0	0
Other Liabilities, Fair Value Disclosure		(19,081)
Total	22,558
Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	2,234,610	2,227,957
Fair Value Measured On Recurring Basis Funds Held Under Reinsurance Agreements Asset Embedded Derivatives	122,194	(22,529)
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Fair Value Measured On Recurring Basis Short Term Investments	3,096	3,346
Other Assets, Fair Value Disclosure	40,659	26,958
Investments, Fair Value Disclosure	0	0
Total	2,400,559	2,235,732
Liabilities, Fair Value Disclosure [Abstract]
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	1,014,228	990,308
Other Liabilities, Fair Value Disclosure		(992,770)
Total	1,015,911
Nonredeemable Preferred Stock [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	39,806	51,123
Nonredeemable Preferred Stock [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	39,806	38,317
Nonredeemable Preferred Stock [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	12,806
Nonredeemable Preferred Stock [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Equity Securities Other Than Non-redeemable Preferred Stock [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	60,346	224,238
Equity Securities Other Than Non-redeemable Preferred Stock [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	60,346	224,238
Equity Securities Other Than Non-redeemable Preferred Stock [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Equity Securities Other Than Non-redeemable Preferred Stock [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Other [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure		11,036
Other [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure		11,036
Other [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure		0
Other [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure		0
Interest Rate Swap [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	51,359	93,508
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(14,311)	(24,374)
Interest Rate Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	51,359	93,508
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(14,311)	(24,374)
Interest Rate Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Foreign Exchange Forward [Member]
Assets, Fair Value Disclosure [Abstract]
Other Assets, Fair Value Disclosure	730
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(7,213)	(5,070)
Foreign Exchange Forward [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Other Assets, Fair Value Disclosure	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Foreign Exchange Forward [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Other Assets, Fair Value Disclosure	730
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(7,213)	(5,070)
Foreign Exchange Forward [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Other Assets, Fair Value Disclosure	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Consumer Price Index Swap [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	(221)
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(1,939)	(262)
Consumer Price Index Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Consumer Price Index Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	(221)
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(1,939)	(262)
Consumer Price Index Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Credit Default Swap [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	5,908	9,136
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(760)	(5)
Credit Default Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Credit Default Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	5,908	9,136
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(760)	(5)
Credit Default Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Equity Option [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	16,932	26,070
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(6,339)	(7,389)
Equity Option [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Equity Option [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	16,932	26,070
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(6,339)	(7,389)
Equity Option [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Currency Swap [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	62,905	100,394
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(6,194)	(3,231)
Currency Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Currency Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	62,905	100,394
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(6,194)	(3,231)
Currency Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	218,541	190,120
Fair Value Option Contractholder Directed Unit Linked Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	217,618	188,891
Fair Value Option Contractholder Directed Unit Linked Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	923	1,229
Fair Value Option Contractholder Directed Unit Linked Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure	0	0
Mortality Swap [Member]
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(1,683)	(2,462)
Mortality Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Mortality Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	0	0
Mortality Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Liabilities, Fair Value Disclosure [Abstract]
Other Liabilities, Fair Value Disclosure	(1,683)	(2,462)
Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	23,210,968	19,619,084
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	0	310,995
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	21,873,696	18,035,836
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	1,337,272	1,272,253
Canadian Provincial Governments [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	4,220,076	3,644,046
Canadian Provincial Governments [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	0	0
Canadian Provincial Governments [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	3,626,134	3,168,081
Canadian Provincial Governments [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	593,942	475,965
Residential Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	1,719,880	1,278,576
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	0	0
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	1,611,998	1,118,285
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	107,882	160,291
Asset-backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	1,648,362	1,429,344
Asset-backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	0	0
Asset-backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	1,524,888	1,210,064
Asset-backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	123,474	219,280
Commercial Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	1,303,387	1,363,654
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	0	0
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	1,300,153	1,342,509
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	3,234	21,145
US Treasury and Government [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	1,943,592	1,468,302
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	1,818,006	1,345,755
US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	103,075	98,059
US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	22,511	24,488
US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	703,428	591,796
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	0	0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	662,225	550,130
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	41,203	41,666
Foreign Government Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	3,401,127	2,698,823
Foreign Government Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	0	276,729
Foreign Government Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	3,396,035	2,409,225
Foreign Government Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale	$ 5,092	$ 12,869

Fair Value of Assets and Liab94

Fair Value of Assets and Liabilities (Quantitative Information for Level 3 Inputs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
US States and Political Subdivisions Debt Securities [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 173,579	$ 167,815
US States and Political Subdivisions Debt Securities [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount for Lack of Marketability	1.00%	1.00%
US States and Political Subdivisions Debt Securities [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount for Lack of Marketability	1.00%	1.00%
US States and Political Subdivisions Debt Securities [Member] | Weighted Average [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount for Lack of Marketability	1.00%	1.00%
Corporate Debt Securities [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 22,511	$ 24,488
Corporate Debt Securities [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount for Lack of Marketability	0.00%	0.00%
Corporate Debt Securities [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount for Lack of Marketability	2.00%	2.00%
Corporate Debt Securities [Member] | Weighted Average [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount for Lack of Marketability	1.00%	1.00%
US Government Agencies Debt Securities [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 4,616	$ 4,670
US Government Agencies Debt Securities [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount for Lack of Marketability	0.00%	0.00%
US Government Agencies Debt Securities [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount for Lack of Marketability	1.00%	1.00%
US Government Agencies Debt Securities [Member] | Weighted Average [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount for Lack of Marketability	1.00%	1.00%
Longevity Swap [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 40,659	$ 26,958
Longevity Swap [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	0.00%	0.00%
Fair Value Inputs Mortality Improvement	(10.00%)	(10.00%)
Longevity Swap [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	100.00%	100.00%
Fair Value Inputs Mortality Improvement	10.00%	10.00%
Longevity Swap [Member] | Weighted Average [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	2.00%	2.00%
Fair Value Inputs Mortality Improvement	3.00%	3.00%
Embedded Derivatives In Indexed Annuity [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 861,758	$ 805,672
Embedded Derivatives In Indexed Annuity [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs Option Budget Projection	2.00%	2.00%
Fair Value Inputs Withdrawal	0.00%	0.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate, Low End	0.00%	0.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	0.00%	0.00%
Embedded Derivatives In Indexed Annuity [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs Option Budget Projection	4.00%	4.00%
Fair Value Inputs Withdrawal	5.00%	5.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate, Low End	35.00%	35.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	100.00%	100.00%
Embedded Derivatives In Indexed Annuity [Member] | Weighted Average [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs Option Budget Projection	2.00%	2.00%
Fair Value Inputs Withdrawal	3.00%	3.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate, Low End	9.00%	8.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	2.00%	2.00%
Embedded Derivatives In Variable Annuity [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 152,470	$ 184,636
Embedded Derivatives In Variable Annuity [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk	0.00%	0.00%
Fair Value Inputs Withdrawal	0.00%	0.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate, Low End	0.00%	0.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	0.00%	0.00%
Embedded Derivatives In Variable Annuity [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk	5.00%	5.00%
Fair Value Inputs Withdrawal	7.00%	7.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate, Low End	25.00%	25.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	100.00%	100.00%
Embedded Derivatives In Variable Annuity [Member] | Weighted Average [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk	1.00%	1.00%
Fair Value Inputs Withdrawal	3.00%	3.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate, Low End	5.00%	6.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	1.00%	2.00%
Mortality Swap [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 1,683	$ 2,462
Mortality Swap [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	0.00%	0.00%
Mortality Swap [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	100.00%	100.00%
Mortality Swap [Member] | Weighted Average [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	1.00%	1.00%
Embedded Derivatives In Variable Annuity Contracts [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Assumptions, Expected Volatility Rate	0.00%	0.00%
Embedded Derivatives In Variable Annuity Contracts [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Assumptions, Expected Volatility Rate	27.00%	27.00%
Embedded Derivatives In Variable Annuity Contracts [Member] | Weighted Average [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Assumptions, Expected Volatility Rate	8.00%	14.00%
Total Return Swap [Member] | Funds Withheld At Interest Embedded Derivatives [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 122,194	$ (22,529)
Total Return Swap [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk	0.00%	0.00%
Fair Value Inputs Withdrawal	0.00%	0.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate, Low End	0.00%	0.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	0.00%	0.00%
Fair Value Inputs Credit Rate	2.00%	2.00%
Total Return Swap [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk	5.00%	5.00%
Fair Value Inputs Withdrawal	5.00%	5.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate, Low End	35.00%	35.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	100.00%	100.00%
Fair Value Inputs Credit Rate	4.00%	4.00%
Total Return Swap [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk	1.00%	1.00%
Fair Value Inputs Withdrawal	3.00%	3.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate, Low End	9.00%	8.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	2.00%	2.00%
Fair Value Inputs Credit Rate	2.00%	2.00%

Fair Value of Assets and Liab95

Fair Value of Assets and Liabilities (Fair Value Assets Transfers between Level 1 and Level 2) (Details) - Available-for-sale Securities [Member] $ in Thousands	Dec. 31, 2017USD ($)
Corporate Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 596,809
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	88,674
Foreign Government Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	317,640
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	$ 0

Fair Value of Assets and Liab96

Fair Value of Assets and Liabilities (Changes in Level 3 Assets and Liabilities) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Corporate Debt Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period		$ 1,272,253		$ 1,226,970	$ 1,310,427
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(6,719)		10,022	(32,452)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		408,995		312,720	243,871	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		(89,248)		(60,399)	3,949	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(285,958)		(195,016)	279,495	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		47,360		14,098	15,455
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		12,973		28,987	(20,556)
Fair Value, Asset Value, End of period		1,337,272		1,272,253	1,226,970
Canadian Provincial Governments [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period		475,965		416,076	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		104,797		47,692	70,144
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0	343,144
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0	0
Fair Value, Asset Value, End of period		593,942		475,965	416,076
Residential Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period		160,291		330,649	188,094
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		2,341		(1,621)	(944)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		76,792		103,553	249,208	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		(28,043)		(167,684)	985	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(18,988)		(38,495)	39,494	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		9,100		1,728	2,853
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		93,994		65,091	(66,113)
Fair Value, Asset Value, End of period		107,882		160,291	330,649
Asset-backed Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period		219,280		303,836	572,960
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		7,044		(2,696)	(2,490)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		45,215		138,522	229,220	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		(38,681)	13,105	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(87,328)		(61,770)	98,918	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		85,152		56,105	13,542
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		147,910		177,938	(402,707)
Fair Value, Asset Value, End of period		123,474		219,280	303,836
US Treasury and Government [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period		24,488		26,265	28,529
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		19		39	(602)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		465	[1]	508	544	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0	[1]	0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		2,000	[1]	(1,837)	1,925	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0	0
Fair Value, Asset Value, End of period		22,511		24,488	26,265
US States and Political Subdivisions Debt Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period		41,666		38,342	42,711
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(15)		962	(3,055)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0	[1]	6,952	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0	[1]	0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		843	[1]	(599)	492	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		7,294		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(6,844)		4,206	(835)
Fair Value, Asset Value, End of period		41,203		41,666	38,342
Foreign Government Debt Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period		12,869		14,065	19,663
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(252)		110	(7)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		496	[1]	0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0	[1]	0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		672	[1]	(1,306)	1,258	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(7,348)		0	(4,333)
Fair Value, Asset Value, End of period		5,092		12,869	14,065
Commercial Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period		21,145		68,563	86,746
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(71)		(5,887)	(337)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0	[1]	1,545	42	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		3,720	[1]	(41,143)	6,153	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		5,404	[1]	(552)	7,226	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		1,302		0	12,828
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(10,132)		2,182	(15,417)
Fair Value, Asset Value, End of period		3,234		21,145	68,563
Funds Withheld At Interest Embedded Derivatives [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period		(22,529)		(76,698)	22,094
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		0		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					0
Fair Value, Asset Value, End of period		122,194		(22,529)	(76,698)
Nonredeemable Preferred Stock [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period				0	7,904
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)					(412)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]				4,529
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					(12,021)
Fair Value, Asset Value, End of period					0
Longevity Swap [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period		26,958		14,996	7,727
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		4,343		(1,133)	(959)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					0
Fair Value, Asset Value, End of period		40,659		26,958	14,996
Short-term Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Asset Value, Beginning of period		3,346		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		11		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	3,703		3,365
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[1]	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]	335		19
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(3,629)		0
Fair Value, Asset Value, End of period		3,096		3,346	0
Interest Sensitive Contract Liabilities Embedded Derivatives [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales		0		0	0
Fair Value, Liability Value, Beginning of period		990,308		1,070,584	1,085,166
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)		0		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases		(55,237)		(12,725)	42,798	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements		79,213		74,458	71,131	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3					0
Fair Value, Liability Value, End of period		1,014,228		990,308	1,070,584
Mortality Swap [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales		0		0	0
Fair Value, Liability Value, Beginning of period		(2,462)		2,619	(797)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)		0		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases		0		0	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements		1,700		329	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3					0
Fair Value, Liability Value, End of period		(1,683)		(2,462)	2,619
Investment Income [Member] | Corporate Debt Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(1,429)		(2,399)	(3,517)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(1,457)		(2,343)	(3,396)
Investment Income [Member] | Canadian Provincial Governments [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		13,180		12,197	2,788
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		13,180		12,197	2,788
Investment Income [Member] | Residential Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(346)		(595)	(1,754)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(196)		(158)	(1,753)
Investment Income [Member] | Asset-backed Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		1,776		801	4,526
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		669		734	2,465
Investment Income [Member] | US Treasury and Government [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(461)		(487)	(48)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(461)		(487)	(48)
Investment Income [Member] | US States and Political Subdivisions Debt Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(55)		215	32
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(54)		215	32
Investment Income [Member] | Foreign Government Debt Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(1)		0	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(1)		0	0
Investment Income [Member] | Commercial Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		709		1,677	2,817
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		1,552	2,718
Investment Income [Member] | Short-term Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0
Investment Related Gains Losses [Member] | Corporate Debt Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		4,991		(4,756)	(2,814)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(5,389)		(817)	(2,278)
Investment Related Gains Losses [Member] | Canadian Provincial Governments [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0	0
Investment Related Gains Losses [Member] | Residential Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		729		(2,153)	(216)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(346)		(231)	0
Investment Related Gains Losses [Member] | Asset-backed Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		245		1,101	808
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0	0
Investment Related Gains Losses [Member] | US Treasury and Government [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0	(233)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0
Investment Related Gains Losses [Member] | US States and Political Subdivisions Debt Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0	(19)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0
Investment Related Gains Losses [Member] | Foreign Government Debt Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0
Investment Related Gains Losses [Member] | Commercial Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(595)		(876)	(4,737)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					(3,593)
Investment Related Gains Losses [Member] | Funds Withheld At Interest Embedded Derivatives [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		144,723		54,169	(98,792)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		144,723		54,169	(98,792)
Investment Related Gains Losses [Member] | Nonredeemable Preferred Stock [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings					0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0
Investment Related Gains Losses [Member] | Longevity Swap [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0	0
Investment Related Gains Losses [Member] | Short-term Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0
Investment Related Gains Losses [Member] | Interest Sensitive Contract Liabilities Embedded Derivatives [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		(32,166)		(7,834)	33,191
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		23,472		(4,579)	(43,496)
Investment Related Gains Losses [Member] | Mortality Swap [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		0		0	0
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0	0
Interest Income [Member] | Funds Withheld At Interest Embedded Derivatives [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0	0
Interest Income [Member] | Nonredeemable Preferred Stock [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings					0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0
Interest Income [Member] | Longevity Swap [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0	0
Interest Income [Member] | Interest Sensitive Contract Liabilities Embedded Derivatives [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		80,062		(10,709)	(19,440)
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(159,276)		(63,748)	(51,691)
Interest Income [Member] | Mortality Swap [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		0		0	0
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0	0
Other Income [Member] | Funds Withheld At Interest Embedded Derivatives [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0			0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0			0
Other Income [Member] | Nonredeemable Preferred Stock [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings					0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0
Other Income [Member] | Longevity Swap [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		9,358		13,095	8,228
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		9,358		13,095	8,228
Other Income [Member] | Interest Sensitive Contract Liabilities Embedded Derivatives [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		0		0	0
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0			0
Other Income [Member] | Mortality Swap [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		(921)		172	(1,822)
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		$ (921)		$ (172)	$ 1,822
[1]	The amount reported within purchases, sales and settlements is the purchase price (for purchases) and the sales/settlement proceeds (for sales and settlements) based upon the actual date purchased or sold/settled. Items purchased and sold/settled in the same period are excluded from the rollforward. The Company had no issuances during the period.

Fair Value of Assets and Liab97

Fair Value of Assets and Liabilities (Fair Value Assets Measured on Non-Recurring Basis) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Private Equity Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets Carrying Value Prior To Impairment	[1]	$ 106	$ 0
Fair Value Assets Gains Losses	[1]	(531)	0
Partnership Interest [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets Carrying Value Prior To Impairment	[2]	4,656	6,192
Fair Value Assets Gains Losses	[2]	$ (7,204)	$ (9,277)
[1]	The fair value of the Company’s private equity investments is based on external valuation models.
[2]	The impaired limited partnership interests presented above were accounted for using the cost method. Impairments on these cost method investments were recognized at estimated fair value determined using the net asset values of the Company’s ownership interest as provided in the financial statements of the investees. The market for these investments has limited activity and price transparency

Fair Value of Assets and Liab98

Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		$ 4,400,533	$ 3,775,522
Policy loans		1,357,624	1,427,602
Funds withheld at interest		6,083,388	5,875,919
Cash and cash equivalents		1,303,524	1,200,718	$ 1,525,275	$ 1,645,669
Short-term investments		93,304	76,710
Other invested assets		1,605,484	1,591,940
Accrued investment income		392,721	347,173
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities		16,227,642	14,029,354
Collateral finance and securitization notes		783,938	840,700
Carrying Value [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		4,400,533	3,775,522
Policy loans		1,357,624	1,427,602
Funds withheld at interest	[1]	5,955,092	5,893,381
Cash and cash equivalents		946,736	862,117
Short-term investments		42,558	32,469
Other invested assets		690,198	477,132
Accrued investment income		392,721	347,173
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	12,683,872	10,225,099
Long And Short Term Debt		2,788,365	3,088,635
Collateral finance and securitization notes		783,938	840,700
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		4,477,654	3,786,987
Policy loans		1,357,624	1,427,602
Funds withheld at interest	[1]	6,275,623	6,193,166
Cash and cash equivalents		946,736	862,117
Short-term investments		42,558	32,469
Other invested assets		718,282	510,640
Accrued investment income		392,721	347,173
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	12,917,243	10,234,544
Long And Short Term Debt		2,959,912	3,186,173
Collateral finance and securitization notes		722,145	745,805
Estimate of Fair Value Measurement [Member] | Net Asset Value [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		0	0
Policy loans		0	0
Funds withheld at interest	[1]	0	0
Cash and cash equivalents		0	0
Short-term investments		0	0
Other invested assets		335,125	296,773
Accrued investment income		0	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	0	0
Long And Short Term Debt		0	0
Collateral finance and securitization notes		0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		0	0
Policy loans		0	0
Funds withheld at interest	[1]	0	0
Cash and cash equivalents		946,736	862,117
Short-term investments		42,558	32,469
Other invested assets		28,540	26,294
Accrued investment income		0	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	0	0
Long And Short Term Debt		0	0
Collateral finance and securitization notes		0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		0	0
Policy loans		1,357,624	1,427,602
Funds withheld at interest	[1]	0	0
Cash and cash equivalents		0	0
Short-term investments		0	0
Other invested assets		67,778	55,669
Accrued investment income		392,721	347,173
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	0	0
Long And Short Term Debt		0	0
Collateral finance and securitization notes		0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		4,477,654	3,786,987
Policy loans		0	0
Funds withheld at interest	[1]	6,275,623	6,193,166
Cash and cash equivalents		0	0
Short-term investments		0	0
Other invested assets		286,839	131,904
Accrued investment income		0	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	12,917,243	10,234,544
Long And Short Term Debt		2,959,912	3,186,173
Collateral finance and securitization notes		$ 722,145	$ 745,805
[1]	Carrying values presented herein may differ from those in the Company’s consolidated balance sheets because certain items within the respective financial statement captions may be measured at fair value on a recurring basis.

Fair Value of Assets and Liab99

Fair Value of Assets and Liabilities (Narrative) (Details)	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Percentage Of Fixed Maturity Securities Classified As Level 3	5.90%	6.90%

Reinsurance Reinsurance (Ceded

Reinsurance Reinsurance (Ceded Reinsurance Receivable Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 782,027	$ 683,972
Reinsurance Recoverables, Percentage of Total	100.00%	100.00%
Other Reinsurers [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 127,808	$ 118,679
Reinsurance Recoverables, Percentage of Total	16.20%	17.30%
AM Best, A+ Rating [Member] | Reinsurer A [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 301,478	$ 240,894
Reinsurance Recoverables, Percentage of Total	38.60%	35.20%
AM Best, A+ Rating [Member] | Reinsurer B [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 203,898	$ 183,881
Reinsurance Recoverables, Percentage of Total	26.10%	26.90%
AM Best, A+ Rating [Member] | Reinsurer C [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 67,723	$ 68,832
Reinsurance Recoverables, Percentage of Total	8.70%	10.10%
AM Best, A++ Rating [Member] | Reinsurer D [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 40,592	$ 36,202
Reinsurance Recoverables, Percentage of Total	5.20%	5.30%
AM Best, A Rating [Member] | Reinsurer E [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 40,528	$ 35,484
Reinsurance Recoverables, Percentage of Total	5.20%	5.20%

Reinsurance (Effect of Reinsura

Reinsurance (Effect of Reinsurance on Net Premiums and Claims and Other Policy Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Premiums Earned, Net [Abstract]
Direct Premiums Earned	$ 61,571	$ 57,562	$ 43,106
Assumed Premiums Earned	10,642,462	10,049,587	9,371,308
Ceded Premiums Earned	(862,903)	(858,278)	(843,673)
Net premiums	9,841,130	9,248,871	8,570,741
Policyholder Benefits and Claims Incurred, Net [Abstract]
Policyholder Benefits and Claims Incurred, Direct	104,447	105,435	82,942
Policyholder Benefits and Claims Incurred, Assumed	9,281,590	8,621,647	8,205,308
Policyholder Benefits and Claims Incurred, Ceded	(867,120)	(733,707)	(798,868)
Claims and other policy benefits	$ 8,518,917	$ 7,993,375	$ 7,489,382

Reinsurance (Effect of Reins102

Reinsurance (Effect of Reinsurance on Life Insurance In Force) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reinsurance Disclosures [Abstract]
Reinsurance Premiums for Insurance Companies, by Product Segment, Gross Amount	$ 1,462	$ 1,576	$ 1,686
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Assumed from Other Companies	3,297,275	3,062,525	2,995,079
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	205,529	214,727	222,388
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 3,093,208	$ 2,849,374	$ 2,774,377
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	106.60%	107.50%	108.00%

Reinsurance (Narrative) (Detail

Reinsurance (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Effects of Reinsurance [Line Items]
Maximum Life Insurance Retention Per Individual Life	$ 8,000
Reinsurance ceded receivables	782,027	$ 683,972
Reinsurance Claims Recoverables	243,800	242,000
Claims Recoverable From Retrocessionaires Past Due	1,900	4,000
Statutory Financial Reinsurance	16,200,000	10,800,000
Statutory Reserves Related To Financial Requirements	2,901,100	1,935,000
Assets Held-in-trust	841,500	893,800
Benefit Of RGA Subsidiaries [Member]
Effects of Reinsurance [Line Items]
Assets Held-in-trust	2,214,100	2,372,100
Benefit Of Third Parties [Member]
Effects of Reinsurance [Line Items]
Assets Held-in-trust	$ 15,584,300	$ 12,135,300
AM Best, A- Rating [Member]
Effects of Reinsurance [Line Items]
Retrocession Pool Participants Minimum AM Best Rating	“A- (excellent)”	“A- (excellent)”

Deferred Policy Acquisition 104

Deferred Policy Acquisition Costs (Movement Analysis Of Deferred Policy Acquisition Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred Policy Acquisition Costs	$ 3,338,605	$ 3,392,437	$ 3,342,575
Deferred Policy Acquisition Costs, Additions	348,470	350,233	352,260
Deferred Policy Acquisition Costs, Amortization Expense	(432,474)	(341,115)	(288,630)
Deferred Policy Acquisition Cost, Amortization Expense, Other	(70,392)	(40,077)	58,754
Deferred Policy Acquisition Cost, Amortization Expense, Unrealized Investment Gains (Losses)	(8,220)	(3,541)	17,510
Deferred Policy Acquisition Cost, Foreign Currency Translation Adjustment	63,835	(19,332)	(90,032)
Deferred Policy Acquisition Costs	$ 3,239,824	$ 3,338,605	$ 3,392,437

Deferred Policy Acquisition 105

Deferred Policy Acquisition Costs Deferred Policy Acquisition Costs (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017
Deferred Policy Acquisition Costs Disclosures [Abstract]
Nature of Deferred Policy Acquisition Costs	Some reinsurance agreements involve reimbursing the ceding company for allowances and commissions in excess of first-year premiums. These amounts represent acquisition costs and are capitalized to the extent deemed recoverable from the future premiums and amortized against future profits of the business.
Type of Deferred Policy Acquisition Costs	This type of agreement presents a risk to the extent that the business lapses faster than originally anticipated, resulting in future profits being insufficient to recover the Company’s investment.

Income Tax (Pre-tax Income Fore

Income Tax (Pre-tax Income Foreign and Domestic) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income (Loss) from Continuing Operations before Income Taxes, Domestic									$ 870,532	$ 758,496	$ 493,328
Income (Loss) from Continuing Operations before Income Taxes, Foreign									272,283	285,450	251,467
Income before income taxes	$ 255,494	$ 340,162	$ 339,315	$ 207,844	$ 295,543	$ 287,600	$ 353,223	$ 107,580	$ 1,142,815	$ 1,043,946	$ 744,795

Income Tax (Provision for Incom

Income Tax (Provision for Income Tax Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current Federal Tax Expense (Benefit)	$ 131,108	$ 1,020	$ 1,588
Current Foreign Tax Expense (Benefit)	36,830	47,706	92,045
Current Income Tax Expense (Benefit)	167,938	48,726	93,633
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred Federal Income Tax Expense (Benefit)	159,853	273,928	193,204
Tax Adjustments, Settlements, and Unusual Provisions	(1,033,755)	0	0
Deferred Foreign Income Tax Expense (Benefit)	26,598	19,849	(44,208)
Deferred income taxes	(847,304)	293,777	148,996
Income Tax Expense (Benefit)	$ (679,366)	$ 342,503	$ 242,629

Income Tax (Provision for In108

Income Tax (Provision for Income Tax Expense Computed from Statutory Rate to Pre-tax Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Effective Income Tax Rate Reconciliation, Equity in Earnings (Losses) of Unconsolidated Subsidiary, Amount	$ (10,532)	$ 0	$ 0
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	399,985	365,381	260,678
Tax Adjustments, Settlements, and Unusual Provisions	(1,033,755)	0	0
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	(21,867)	(13,974)	(9,950)
Income Tax Reconciliation Foreign Income Tax Basis Differential	(23,324)	(17,770)	(32,472)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	29,458	10,963	19,157
Effective Income Tax Rate Reconciliation, Tax Contingency, Domestic, Amount	(7,184)	111	88
Income Tax Reconciliation Change In Foreign Enacted Tax Rate	(6,065)	0	0
Income Tax Reconciliation Subpart F	1,528	1,783	3,473
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount	(1,681)	(1,683)	(1,936)
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount	(4,674)	(1,473)	1,482
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	(1,255)	(835)	2,109
Income Tax Expense (Benefit)	$ (679,366)	$ 342,503	$ 242,629
Effective Income Tax Rate Reconciliation, Percent	(59.40%)	32.80%	32.60%

Income Tax (Total Income Taxes

Income Tax (Total Income Taxes Provided) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Effects Allocated Directly to Equity [Abstract]
Income Tax Expense (Benefit)	$ (679,366)	$ 342,503	$ 242,629
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	306,849	157,929	(339,889)
Income Tax Effects Allocated Directly to Equity, Employee Stock Options	0	(162)	(2,963)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	(42,153)	21,081	16,478
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	404	1,772	1,726
Income Tax Expense (Benefit), Intraperiod Tax Allocation	$ (414,266)	$ 523,123	$ (82,019)

Income Tax (Tax Effects of Temp

Income Tax (Tax Effects of Temporary Differences that Give Rise to Significant Portions of the Deferred Income Tax Asset and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets, Net [Abstract]
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals	$ 80,905	$ 125,879
Deferred Tax Assets Reinsurance Transactions	96,043	87,688
Deferred Tax Assets Cash And Invested Assets	557	775
Deferred Tax Assets Investment Income	43,230	35,192
Deferred Tax Assets Deferred Acquisition Costs Capitalized For Tax	88,531	143,003
Deferred Tax Assets, Operating Loss Carryforwards	535,374	325,806
Deferred Tax Assets Deferred Acquisition Costs Capitalized For Financial Reporting	102,143	101,223
Deferred Tax Assets, Gross	946,783	819,566
Deferred Tax Assets, Valuation Allowance	(226,884)	(133,354)
Deferred Tax Assets, Net	719,899	686,212
Deferred Tax Liabilities [Abstract]
Deferred Tax Liabilities, Deferred Expense, Deferred Policy Acquisition Cost	627,378	1,013,642
Deferred Tax Liabilities Reinsurance Transactions	1,547,101	1,773,929
Deferred Tax Liabilities Cash And Invested Assets	674,569	505,841
Deferred Tax Liabilities Investment Income	1,858	5,635
Deferred Tax Liabilities, Unrealized Currency Transaction Gains	33,803	91,067
Deferred Tax Liabilities, Prepaid Expenses	0	0
Deferred Tax Liabilities	2,884,709	3,390,114
Net deferred income tax liabilities	2,164,810	2,703,902
Balance Sheet Presentation Of Deferred Tax Liabilities [Abstract]
Deferred Tax Assets, Other	33,499	66,738
Deferred income taxes	$ 2,198,309	$ 2,770,640

Income Tax (Reconciliation of t

Income Tax (Reconciliation of the Amount of Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits Beginning balance, January 1	$ 297,290	$ 296,213	$ 274,661
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions	247,596	226,720	26,170
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions	(246,894)	(229,719)	(7,820)
Unrecognized Tax Benefits, Increases Resulting from Current Period Tax Positions	36,438	4,186	3,396
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	(13,206)	(110)	(194)
Unrecognized Tax Benefits Ending balance, December 31	$ 321,224	$ 297,290	$ 296,213

Income Tax (Narrative) (Details

Income Tax (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets Income Tax Credits And Adjustments Subject To Expiration	$ 65,100
Valuation Allowance Related To Tax Cuts And Jobs Act Of 2017	58,900
Foreign Tax Credits Impact On Uncertain Tax Liabilities	57,000
Foreign Currency Translation Adjustment On Valuation Allowance	10,600
Reclassifications With Other Deferred Tax Assets On Valuation Allowance	(5,600)
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	25,900	$ 21,300
Cash paid for income taxes	48,700	68,000	$ 178,400
Tax Adjustments, Settlements, and Unusual Provisions	(1,033,755)	0	0
Deferred Tax Assets, Valuation Allowance	226,884	133,354
Proceeds from Income Tax Refunds	11,600	6,900	136,800
Deferred Tax Liability Not Recognized, Amount of Unrecognized Deferred Tax Liability	1,442,900	1,147,200
Tax Credit Carryforward, Valuation Allowance	65,100
Operating Loss Carryforwards	2,715,800	1,353,600
Income Tax Credits and Adjustments	152,000	100,900
Unrecognized Tax Benefits	321,224	297,290	296,213	$ 274,661
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	10,900
Unrecognized Tax Benefits, Interest on Income Taxes Expense	(5,000)	(8,400)	$ 8,200
Income Tax Examination, Penalties Expense		300
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	15,100	$ 20,400
Tax Year 2029 [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	181,200
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	181,200
Tax Year 2030 [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	451,400
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	451,400
Tax Year 2032 [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	1,557,100
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	1,557,100
TaxYear20342036 [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	48,000
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	48,000
Foreign Tax Authority [Member] | Australian Taxation Office [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	20,100
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	3,300
Foreign Tax Authority [Member] | Revenue Commissioners, Ireland [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	$ 29,900

Employee Benefit Plans (Schedul

Employee Benefit Plans (Schedule of Changes in Projected Benefit Obligations) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, Beginning Balance		$ 161,955
Defined Benefit Plan, Benefit Obligation, Ending Balance		172,143		$ 161,955
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, Beginning Balance		161,955		142,239
Defined Benefit Plan, Service Cost		10,686		10,319		$ 9,222
Defined Benefit Plan, Interest Cost		5,326		4,790		5,035
Defined Benefit Plan, Contributions by Plan Participants (Deprecated 2017-01-31)		0		0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	[2]	159	[1]	0	[1]	0
Defined Benefit Plan, Actuarial Net (Gains) Losses		11,336		9,973
Defined Benefit Plan Settlement Gain Loss		(438)		258
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		(12,907)		3,152
Defined Benefit Plan, Benefits Paid (Deprecated 2017-01-31)		(5,974)		(3,047)
Defined Benefit Plan, Foreign Currency Exchange Rate Changes, Benefit Obligation		2,000		575
Defined Benefit Plan, Benefit Obligation, Ending Balance		172,143		161,955		142,239
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, Beginning Balance		60,524		63,307
Defined Benefit Plan, Service Cost		2,543		2,883		4,062
Defined Benefit Plan, Interest Cost		2,118		2,259		2,572
Defined Benefit Plan, Contributions by Plan Participants (Deprecated 2017-01-31)		354		305
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	[2]	0	[1]	(13,743)	[1]	0
Defined Benefit Plan, Actuarial Net (Gains) Losses		5,510		6,228
Defined Benefit Plan Settlement Gain Loss		0		0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		0		0
Defined Benefit Plan, Benefits Paid (Deprecated 2017-01-31)		(851)		(715)
Defined Benefit Plan, Foreign Currency Exchange Rate Changes, Benefit Obligation		0		0
Defined Benefit Plan, Benefit Obligation, Ending Balance		$ 70,198		$ 60,524		$ 63,307
[1]	Reflects effect of the amendment to RGA’s U.S. retiree health care benefit plan announced in 2016, effective January 1, 2017 and other administrative amendments to the pension plans. The amounts were recorded in AOCI and will be amortized through prior service cost.
[2]	Reflects effect of the amendment to RGA’s U.S. retiree health care benefit plan announced in 2016, effective January 1, 2017 and other administrative amendments to the pension plans. The amounts were recorded in AOCI and will be amortized through prior service cost.

Employee Benefit Plans (Sche114

Employee Benefit Plans (Schedule of Changes in Fair Value of Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	$ 84,770
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance	103,236	$ 84,770
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(68,907)	(77,185)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	84,770	68,435
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	14,481	6,584
Defined Benefit Plan, Plan Assets, Contributions by Employer	22,866	15,950
Defined Benefit Plan, Contributions by Plan Participants (Deprecated 2017-01-31)	0	0
Defined Benefit Plan, Plan Assets, Payment for Settlement	(12,907)	(3,152)
Defined Benefit Plan, Benefits Paid (Deprecated 2017-01-31)	(5,974)	(3,047)
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance	103,236	84,770
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(68,907)	(77,185)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	0	0
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	0	0
Defined Benefit Plan, Plan Assets, Contributions by Employer	497	410
Defined Benefit Plan, Contributions by Plan Participants (Deprecated 2017-01-31)	354	305
Defined Benefit Plan, Plan Assets, Payment for Settlement	0	0
Defined Benefit Plan, Benefits Paid (Deprecated 2017-01-31)	(851)	(715)
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance	0	0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	$ (70,198)	$ (60,524)

Employee Benefit Plans (Sche115

Employee Benefit Plans (Schedule of Net Funded Status) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		$ 103,236	$ 84,770
Defined Benefit Plan, Benefit Obligation		172,143	161,955
Defined Benefit Plan, Funded Status of Plan, Total		(68,907)	(77,185)
Qualified Plan [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		103,236	84,770
Defined Benefit Plan, Benefit Obligation		107,072	96,418
Defined Benefit Plan, Funded Status of Plan, Total		(3,836)	(11,648)
Nonqualified Plan [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0	0
Defined Benefit Plan, Benefit Obligation	[1]	65,071	65,537
Defined Benefit Plan, Funded Status of Plan, Total	[1]	$ (65,071)	$ (65,537)
[1]	For non-qualified plans, there are no required funding levels.

Employee Benefit Plans (Sche116

Employee Benefit Plans (Schedule of Amounts Recognized in Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	$ 40,058	$ 46,119
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Prior Service Costs (Credit) Arising During Period, Net of Tax	804	703
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	40,862	46,822
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	35,672	32,156
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Prior Service Costs (Credit) Arising During Period, Net of Tax	(11,806)	(13,121)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	$ 23,866	$ 19,035

Employee Benefit Plans (Sche117

Employee Benefit Plans (Schedule of Projected Benefit Obligations in Excess of Fair Value of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Defined Benefit Plan, Benefit Obligation	$ 172,143	$ 161,955
Defined Benefit Plan, Fair Value of Plan Assets	$ 103,236	$ 84,770

Employee Benefit Plans (Sche118

Employee Benefit Plans (Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation	$ 169,705	$ 158,580
Defined Benefit Plan, Fair Value of Plan Assets	$ 103,236	$ 84,770

Employee Benefit Plans (Compone

Employee Benefit Plans (Components of Net Periodic Benefit Cost Recognized in Other Comprehensive Income) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		$ (10,587)		$ 4,427		$ 4,618
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		(11,717)		(444)		(337)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Benefit Plan, Service Cost		10,686		10,319		9,222
Defined Benefit Plan, Interest Cost		5,326		4,790		5,035
Defined Benefit Plan, Expected Return (Loss) on Plan Assets		(6,215)		(5,138)		(4,897)
Defined Benefit Plan, Amortization of Gain (Loss)		4,382		4,323		3,429
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		344		294		309
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement		(4,785)		(1,026)		0
Defined Benefit Plan, Net Periodic Benefit Cost, Total		19,308		15,614		13,098
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax		2,633		8,785		5,774
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		(4,382)		(4,323)		(3,429)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		(344)		(294)		(309)
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax		(4,785)		(1,026)		0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	[2]	159	[1]	0	[1]	0
Other Comprehensive Income Defined Benefit Plan Net Foreign Exchange Translations And Other Adjustments		759		707		(1,797)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax		(5,960)		3,849		239
Defined Benefit Plan Net Periodic Benefit Cost And Other Comprehensive Income Defined Benefit Plans Adjustment Before Tax Period Increase Decrease		13,348		19,463		13,337
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Benefit Plan, Service Cost		2,543		2,883		4,062
Defined Benefit Plan, Interest Cost		2,118		2,259		2,572
Defined Benefit Plan, Expected Return (Loss) on Plan Assets		0		0		0
Defined Benefit Plan, Amortization of Gain (Loss)		1,992		1,827		2,465
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		(1,315)		(622)		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement		0		0		0
Defined Benefit Plan, Net Periodic Benefit Cost, Total		5,338		6,347		9,099
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax		5,507		6,228		(2,729)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		(1,992)		(1,827)		(2,465)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		1,315		622		0
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax		0		0		0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	[2]	0	[1]	(13,743)	[1]	0
Other Comprehensive Income Defined Benefit Plan Net Foreign Exchange Translations And Other Adjustments		0		0		0
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax		4,830		(8,720)		(5,194)
Defined Benefit Plan Net Periodic Benefit Cost And Other Comprehensive Income Defined Benefit Plans Adjustment Before Tax Period Increase Decrease		$ 10,168		$ (2,373)		$ 3,905
[1]	Reflects effect of the amendment to RGA’s U.S. retiree health care benefit plan announced in 2016, effective January 1, 2017 and other administrative amendments to the pension plans. The amounts were recorded in AOCI and will be amortized through prior service cost.
[2]	Reflects effect of the amendment to RGA’s U.S. retiree health care benefit plan announced in 2016, effective January 1, 2017 and other administrative amendments to the pension plans. The amounts were recorded in AOCI and will be amortized through prior service cost.

Employee Benefit Plans (Sche120

Employee Benefit Plans (Schedule of Expected Future Benefit Payments) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	$ 9,315
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	9,765
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	10,885
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	11,102
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	13,184
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	69,285
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	1,238
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	1,495
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	1,842
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	2,188
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	2,521
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	$ 18,205

Employee Benefit Plans (Sche121

Employee Benefit Plans (Schedule of Assumptions Used Calculating Benefit Obligations) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Assumptions Used in Calculations [Abstract]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.40%	3.80%	3.99%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	3.81%	3.95%	3.77%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	7.35%	7.35%	7.35%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	4.16%	4.08%	4.08%
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Assumptions Used in Calculations [Abstract]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.56%	4.10%	4.43%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	4.10%	4.43%	4.05%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	0.00%	0.00%	0.00%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	0.00%	0.00%	0.00%

Employee Benefit Plans (Sche122

Employee Benefit Plans (Schedule of Health Care Costs Trend Rates) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Medicare Eligible Claims [Member]
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year	10.00%	8.00%
Defined Benefit Plan, Assumed Health Care Cost Trend Rate, Description	9% down to 5% in 2024	10% down to 5% in 2024
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate	2,024	2,020
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	5.00%	5.00%
Pre Medicare Eligible Claims [Member]
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year	10.00%	8.00%
Defined Benefit Plan, Assumed Health Care Cost Trend Rate, Description	9% down to 5% in 2024	10% down to 5% in 2024
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate	2,024	2,020
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	5.00%	5.00%

Employee Benefit Plans (Sche123

Employee Benefit Plans (Schedule of Effect of One Percentage Point Change in Assumed Health Care Cost Trend Rates) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Retirement Benefits [Abstract]
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components	$ 7,941
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components	(7,104)
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation	447
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation	$ (359)

Employee Benefit Plans (Sche124

Employee Benefit Plans (Schedule of Allocation of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017		Dec. 31, 2016
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 103,236		$ 84,770
Mutual Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 103,106	[1]	$ 84,671	[2]
U.S. Equity Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	27.00%		28.00%
U.S. Fixed Income Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	36.00%		37.00%
Non-U.S. Equity Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	22.00%		20.00%
Other [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	15.00%		15.00%
Cash and Cash Equivalents [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 130		$ 99
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	103,236		84,770
Fair Value, Inputs, Level 1 [Member] | Mutual Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	103,106	[1]	84,671	[2]
Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	130		99
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Fair Value, Inputs, Level 2 [Member] | Mutual Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[1]	0	[2]
Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Fair Value, Inputs, Level 3 [Member] | Mutual Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[1]	0	[2]
Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 0		$ 0
[1]	Mutual funds were invested 27% in U.S. equity funds, 36% in U.S. fixed income funds, 22% in non-U.S. equity funds and 15% in other.
[2]	Mutual funds were invested 28% in U.S. equity funds, 37% in U.S. fixed income funds, 20% in non-U.S. equity funds and 15% in other.

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation	$ 169,705	$ 158,580
Defined Benefit Plan, Amortization of Net Gains (Losses)	3,400
Defined Benefit Plan, Amortization of Net Prior Service Cost (Credit)	1,100
Defined Contribution Plan, Cost	14,200	9,900	$ 9,000
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	19,308	15,614	13,098
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	14,500
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	5,338	$ 6,347	$ 9,099
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	$ 1,200
Debt Securities [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities	40.00%
Equity Securities [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities	60.00%

Financial Condition and Net 126

Financial Condition and Net Income on a Statutory Basis - Significant Subsidiaries (Statutory Accounting Practices Disclosure) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
RGA Reinsurance [Member]
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance		$ 1,584,007	$ 1,521,644
Statutory Accounting Practices, Statutory Net Income Amount		138,359	148,576	$ (23,615)
RCM [Member]
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance		1,557,453	1,651,274
Statutory Accounting Practices, Statutory Net Income Amount		(183,136)	272,038	51,041
RGA Canada [Member]
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance		1,006,190	915,134
Statutory Accounting Practices, Statutory Net Income Amount		25,971	13,947	113,526
RGA Barbados [Member]
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	[1]	1,278,006	957,051
Statutory Accounting Practices, Statutory Net Income Amount	[1]	309,346	95,859	113,049
RGA Australia [Member]
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance		476,528	370,039
Statutory Accounting Practices, Statutory Net Income Amount		78,497	(7,694)	(18,128)
RGA Atlantic [Member]
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance		812,307	596,016
Statutory Accounting Practices, Statutory Net Income Amount		213,511	110,172	132,192
RGA Americas [Member]
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	[1]	4,833,890	3,752,910
Statutory Accounting Practices, Statutory Net Income Amount	[1]	624,145	282,226	264,518
Other Reinsurance Subsidiaries [Member]
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance		2,694,317	2,224,833
Statutory Accounting Practices, Statutory Net Income Amount		$ 65,658	$ 130,289	$ 300,847
[1]	In 2017, the Company contributed to RGA Americas Reinsurance Company, Ltd. all of the outstanding shares of its wholly-owned subsidiary, RGA Australia. Periods prior to 2017 have been adjusted to reflect this contribution.

Financial Condition and Net 127

Financial Condition and Net Income on a Statutory Basis - Significant Subsidiaries (Reconciliation of NAIC SAP and Prescribed Practice) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statutory Basis [Abstract]
Prescribed Practice Surplus Note	$ 726,531	$ 574,574
Prescribed Practice Letters Of Credit	(960,100)	(615,100)
Surplus Deficit NAIC SAP	$ (233,569)	$ (40,526)

Financial Condition and Net 128

Financial Condition and Net Income on a Statutory Basis - Significant Subsidiaries (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Statutory Basis [Abstract]
Number Of Preceeding Months To Accumulate Dividend Paid For Approval	12 months
Future Dividend Payment Restricted To Such Percent Of Surplus To Policy Holders	10.00%
RGA Reinsurance Max Dividend Payments Without Approval	$ 158.4

Commitments Contingencies an129

Commitments Contingencies and Guarantees (Commitments to Fund Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Limited Partner [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	$ 485,197	$ 332,169
Commercial Loan [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	40,815	126,248
Bank Loan Obligations [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	60,472	58,318
Equity Release Mortgages [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	$ 153,937	$ 130,324

Commitments Contingencies an130

Commitments Contingencies and Guarantees (Schedule of Future Minimum Rental Payments for Operating Leases) (Details) - Property Subject to Operating Lease [Member] $ in Thousands	Dec. 31, 2017USD ($)
Operating Leases, Future Minimum Payments Due [Abstract]
Operating Leases, Future Minimum Payments Due, Current	$ 11,157
Operating Leases, Future Minimum Payments, Due in Two Years	7,108
Operating Leases, Future Minimum Payments, Due in Three Years	4,879
Operating Leases, Future Minimum Payments, Due in Four Years	3,076
Operating Leases, Future Minimum Payments, Due in Five Years	2,421
Operating Leases, Future Minimum Payments, Due Thereafter	$ 9,466

Commitments Contingencies an131

Commitments Contingencies and Guarantees (Maximum Potential Obligation) (Details) $ in Millions	Dec. 31, 2017USD ($)
Commitment Period Two Thousand Twenty Six [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 500
Commitment Period Two Thousand Thirty Three [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	450
Commitment Period Two Thousand Thirty Four [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	2,000
Commitment Period Two Thousand Thirty Five [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	1,314.2
Commitment Period Two Thousand Thirty Six [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	2,932
Commitment Period Two Thousand Thirty Seven [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 5,750

Commitments Contingencies an132

Commitments Contingencies and Guarantees (Guarantees Issued) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Insurance Treaty Guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	$ 1,047,449	$ 902,216
Insurance Treaty Guarantee Net Of Assets Held In Trust [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	926,393	780,786
Guarantee Of Borrowed Securities [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	294,325	263,820
Product Financing Arrangement [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	86,183	119,073
Guarantee Of Lease Obligations [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	$ 1,662	$ 2,428

Commitments Contingencies an133

Commitments Contingencies and Guarantees (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Operating Leases, Rent Expense	$ 15.7	$ 13.7	$ 12.1
Maximum Capital Lease Obligations As Offset Against Industrial Bonds	$ 150

Debt (Schedule of Long-term Deb

Debt (Schedule of Long-term Debt Instruments) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2006
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 2,808,770,000	$ 3,110,853,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	20,405,000	22,218,000
Debt Instrument, Face Amount			$ 850,000,000
Long-term debt	2,788,365,000	3,088,635,000
Senior Notes Due 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	0	299,945,000
Debt Instrument, Face Amount	$ 300,000,000
Debt Instrument, Maturity Date	Dec. 31, 2017
Debt Instrument, Interest Rate, Stated Percentage	5.625%
Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 399,873,000	399,805,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2019
Debt Instrument, Interest Rate, Stated Percentage	6.45%
Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 399,245,000	399,025,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2021
Debt Instrument, Interest Rate, Stated Percentage	5.00%
Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 399,138,000	398,986,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2023
Debt Instrument, Interest Rate, Stated Percentage	4.70%
Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 399,987,000	399,985,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	8,800,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2026
Debt Instrument, Interest Rate, Stated Percentage	3.95%
Subordinated Debentures Due 2042 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 400,000,000	400,000,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2042
Debt Instrument, Interest Rate, Stated Percentage	6.20%
Subordinated Debentures Due 2056 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 400,000,000	400,000,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2056
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Junior Subordinated Debentures Due 2065 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 318,740,000	318,737,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2065
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 91,787,000	$ 94,370,000
Debt Instrument, Face Amount	$ 100,000,000
Debt Instrument, Maturity Date	Dec. 31, 2039
Debt Instrument, Interest Rate, Stated Percentage	4.09%

Debt Debt (Repayments of Debt)

Debt Debt (Repayments of Debt) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Debt Disclosure [Abstract]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 2,690
Long-term Debt, Maturities, Repayments of Principal in Year Two	402,802
Long-term Debt, Maturities, Repayments of Principal in Year Three	2,919
Long-term Debt, Maturities, Repayments of Principal in Year Four	403,040
Long-term Debt, Maturities, Repayments of Principal in Year Five	3,167
Long-term Debt, Maturities, Repayments of Principal after Year Five	$ 1,996,972

Debt Debt (Schedule of Line of

Debt Debt (Schedule of Line of Credit Facilities) (Details) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,266,500,000
Credit Facility Two Thousand Seventeen [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1]	$ 180,403,000
Syndicated Credit Facility $850 Million [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		Sep. 30, 2019
Line of Credit Facility, Maximum Borrowing Capacity		$ 850,000,000
Long-term Line of Credit	[2]	$ 96,564,000	$ 96,095,000
Line of Credit Facility, Interest Rate Description		Senior unsecured long-term debt rating
Foreign Credit Facility December 2019 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date	[1]	Dec. 31, 2019
Long-term Line of Credit	[1],[2]	$ 117,135,000	72,080,000
Line of Credit Facility, Interest Rate Description	[1]	Fixed
Credit Facility Two Thousand Eighteen [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date	[1]	Nov. 30, 2018
Line of Credit Facility, Maximum Borrowing Capacity	[1]	$ 117,135,000
Long-term Line of Credit	[1],[2]	$ 8,638,000	31,382,000
Line of Credit Facility, Interest Rate Description	[1]	Fixed
Credit Facility Two Thousand Nineteen [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date	[1]	Mar. 31, 2019
Line of Credit Facility, Maximum Borrowing Capacity	[1]	$ 5,952,000
Long-term Line of Credit	[1],[2]	$ 5,952,000	17,513,000
Line of Credit Facility, Interest Rate Description	[1]	Fixed
Credit Facility 100 Million [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		Jun. 30, 2020
Line of Credit Facility, Maximum Borrowing Capacity		$ 100,000,000
Long-term Line of Credit	[2]	$ 75,573,000	70,690,000
Line of Credit Facility, Interest Rate Description		Fixed
Credit Facility 100 Million [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		Oct. 31, 2019
Line of Credit Facility, Maximum Borrowing Capacity		$ 188,000,000
Long-term Line of Credit	[2]	$ 188,000,000	270,000,000
Line of Credit Facility, Interest Rate Description		Fixed
Credit Facility $100 Million 2021 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		May 31, 2021
Line of Credit Facility, Maximum Borrowing Capacity		$ 100,000,000
Long-term Line of Credit	[2]	$ 100,000,000	0
Line of Credit Facility, Interest Rate Description		Fixed
Syndicated Credit Facility $75 Million [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		Jun. 30, 2021
Line of Credit Facility, Maximum Borrowing Capacity		$ 75,000,000
Long-term Line of Credit	[2]	$ 61,900,000	85,040,000
Line of Credit Facility, Interest Rate Description		Fixed
Syndicated Credit Facility $500 Million [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date		May 31, 2022
Line of Credit Facility, Maximum Borrowing Capacity		$ 500,000,000
Long-term Line of Credit	[2]	$ 500,000,000	$ 0
Line of Credit Facility, Interest Rate Description		Fixed
[1]	Foreign currency denominated facility, amounts presented are in U.S. dollars.
[2]	Represents issued but undrawn letters of credit. There was no cash borrowed for the periods presented.

Debt (Narrative) (Details)

Debt (Narrative) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2006
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net		$ 20,405,000	$ 22,218,000
Undrawn Outstanding Letters Of Credit In Favor Of Third Parties		120,100,000	189,400,000
Undrawn Outstanding Letters Of Credit Between Subsidiaries		1,492,200,000	$ 1,010,800,000
Debt Instrument, Face Amount					$ 850,000,000
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,266,500,000
Debt, Weighted Average Interest Rate		5.24%	5.16%
Long-term Debt, Gross		$ 2,808,770,000	$ 3,110,853,000
Long-term debt		2,788,365,000	3,088,635,000
Long-term Debt, Maturities, Repayments of Principal in Year Four		403,040,000
Line of Credit Facility, Commitment Fee Amount		10,500,000	7,900,000	$ 10,900,000
Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net		$ 8,800,000
Debt Instrument, Interest Rate, Stated Percentage		3.95%
Debt Instrument, Maturity Date		Dec. 31, 2026
Debt Instrument, Face Amount		$ 400,000,000
Proceeds from Issuance of Long-term Debt and Capital Securities, Net		791,200,000
Long-term Debt, Gross		$ 399,987,000	399,985,000
Subordinated Debentures Due 2056 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.75%
Debt Instrument, Maturity Date		Dec. 31, 2056
Debt Instrument, Face Amount		$ 400,000,000
Long-term Debt, Gross		$ 400,000,000	400,000,000
Junior Subordinated Debentures Due 2065 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Dec. 31, 2065
Debt Instrument, Face Amount		$ 400,000,000
Long-term Debt, Gross		$ 318,740,000	318,737,000
Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.00%
Debt Instrument, Maturity Date		Dec. 31, 2021
Debt Instrument, Face Amount		$ 400,000,000
Long-term Debt, Gross		$ 399,245,000	399,025,000
Subordinated Debentures Due 2042 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.20%
Debt Instrument, Maturity Date		Dec. 31, 2042
Debt Instrument, Face Amount		$ 400,000,000
Long-term Debt, Gross		$ 400,000,000	400,000,000
Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.70%
Debt Instrument, Maturity Date		Dec. 31, 2023
Debt Instrument, Face Amount		$ 400,000,000
Long-term Debt, Gross		$ 399,138,000	398,986,000
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.09%
Debt Instrument, Maturity Date		Dec. 31, 2039
Debt Instrument, Face Amount		$ 100,000,000
Long-term Debt, Gross		$ 91,787,000	94,370,000
Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.45%
Debt Instrument, Maturity Date		Dec. 31, 2019
Debt Instrument, Face Amount		$ 400,000,000
Long-term Debt, Gross		$ 399,873,000	399,805,000
Senior Notes Due 2017 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.625%
Debt Instrument, Maturity Date		Dec. 31, 2017
Debt Instrument, Face Amount		$ 300,000,000
Long-term Debt, Gross		0	299,945,000
Syndicated Credit Facility $850 Million [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		850,000,000
Long-term Line of Credit	[1]	$ 96,564,000	$ 96,095,000
[1]	Represents issued but undrawn letters of credit. There was no cash borrowed for the periods presented.

Collateral Finance and Secur138

Collateral Finance and Securitization Notes Collateral Finance and Securitization Notes (List of Collateral Finance and Securitization Notes) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Collateralized Financings	$ 783,938	$ 840,700
Debt Issuance Cost	(20,405)	(22,218)
Timerberlake Financial [Member]
Collateralized Financings	411,951	451,880
Reinsurance Group Of America Barbados [Member]
Collateralized Financings	159,100	148,820
Chesterfield Financial Holdings LLC [Member]
Collateralized Financings	217,800	246,300
Debt Issuance Cost	(5,400)
Secured Debt [Member]
Debt Issuance Cost	$ (4,913)	$ (6,300)

Collateral Finance and Secur139

Collateral Finance and Securitization Notes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2006
Collateral Finance Facility [Line Items]
Debt Instrument, Face Amount				$ 850,000,000
Direct investment in subsidiary				$ 112,800,000
Assets Held-in-trust	$ 841,500,000	$ 893,800,000
Amount Held In Debt Service Coverage Account	39,700,000	24,100,000
Collateral Financing Expense	28,636,000	25,827,000	$ 22,644,000
Debt Issuance Cost	20,405,000	22,218,000
RGA Americas [Member]
Collateral Finance Facility [Line Items]
Debt Issuance Cost	2,400,000
Reinsurance Group Of America Barbados [Member]
Collateral Finance Facility [Line Items]
Collateral Financing Expense	$ 4,200,000	4,000,000	2,300,000
Timerberlake Financial [Member]
Collateral Finance Facility [Line Items]
Debt Instrument, Issuance Date	Jun. 1, 2006
Collateral Financing Expense	$ 6,400,000	4,200,000	3,800,000
RGA Barbados [Member]
Collateral Finance Facility [Line Items]
Debt Issuance Cost	1,300,000
Chesterfield Financial Holdings LLC [Member]
Collateral Finance Facility [Line Items]
Debt Instrument, Face Amount	300,000,000
Assets Held-in-trust	19,400,000	22,100,000
Collateral Financing Expense	11,300,000	$ 13,100,000	$ 14,000,000
Debt Issuance Cost	$ 5,400,000
Debt Instrument, Interest Rate, Stated Percentage	4.50%
Minimum [Member]
Collateral Finance Facility [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	$ 35,000,000

Segment Information (Reconcilia

Segment Information (Reconciliation of Revenue from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 3,232,443	$ 3,145,310	$ 3,129,276	$ 3,008,740	$ 3,069,298	$ 2,900,577	$ 3,039,068	$ 2,512,568	$ 12,515,769	$ 11,521,511	$ 10,418,178
US Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									6,100,171	5,964,968	5,465,026
US Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,150,378	840,446	643,865
Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									7,250,549	6,805,414	6,108,891
Canada Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									48,938	46,938	45,034
Canada Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,103,520	1,118,004	1,023,012
Canada Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,152,458	1,164,942	1,068,046
EMEA Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,362,075	1,195,149	1,190,742
EMEA Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									311,071	340,518	286,666
EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,673,146	1,535,667	1,477,408
Asia Pacific Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									2,210,686	1,771,150	1,638,357
Asia Pacific Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									73,775	63,382	56,581
Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									2,284,461	1,834,532	1,694,938
Corporate Segment [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									$ 155,155	$ 180,956	$ 68,895

Segment Information (Reconci141

Segment Information (Reconciliation of Income before Income Taxes from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	$ 255,494	$ 340,162	$ 339,315	$ 207,844	$ 295,543	$ 287,600	$ 353,223	$ 107,580	$ 1,142,815	$ 1,043,946	$ 744,795
US Traditional Segment Reporting Information [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									373,434	371,101	235,771
US Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									401,584	283,380	207,963
Americas [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									775,018	654,481	443,734
Canada Traditional Segment Reporting Information [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									120,218	134,705	124,175
Canada Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									16,643	7,945	13,902
Canada Segment Reporting Information [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									136,861	142,650	138,077
EMEA Traditional Segment Reporting Information [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									70,486	30,059	48,410
EMEA Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									123,514	138,007	108,445
EMEA [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									194,000	168,066	156,855
Asia Pacific Traditional Segment Reporting Information [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									148,786	113,928	105,654
Asia Pacific Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									13,130	4,063	19,619
Asia Pacific [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									161,916	117,991	125,273
Corporate Segment [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest									$ (124,980)	$ (39,242)	$ (119,144)

Segment Information (Reconci142

Segment Information (Reconciliation of Interest Expense from Segments to Consolidated) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Interest expense	$ 146,025	$ 137,623	$ 142,863
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Interest expense	$ 146,025	$ 137,623	$ 142,863

Segment Information (Reconci143

Segment Information (Reconciliation of Depreciation and Amortization from Segment to Consolidated) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	$ 705,964	$ 557,055	$ 395,996
US Traditional Segment Reporting Information [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	284,959	271,732	218,974
US Non-Traditional Segment Reporting Information [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	208,790	155,560	44,275
Americas [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	493,749	427,292	263,249
Canada Traditional Segment Reporting Information [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	24,057	22,170	23,887
Canada Non-Traditional Segment Reporting Information [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	10	11	0
Canada Segment Reporting Information [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	24,067	22,181	23,887
EMEA Traditional Segment Reporting Information [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	35,000	46,562	60,193
EMEA Non-Traditional Segment Reporting Information [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	91	72	0
EMEA [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	35,091	46,634	60,193
Asia Pacific Traditional Segment Reporting Information [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	114,333	45,562	31,955
Asia Pacific Non-Traditional Segment Reporting Information [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	1,448	1,492	217
Asia Pacific [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	115,781	47,054	32,172
Corporate Segment [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	$ 37,276	$ 13,894	$ 16,495

Segment Information (Reconci144

Segment Information (Reconciliation of Assets from Segment to Consolidated) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 60,514,818	$ 53,097,879
US Traditional Segment Reporting Information [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	18,603,423	18,140,825
US Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	15,959,206	13,712,106
Americas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	34,562,629	31,852,931
Canada Traditional Segment Reporting Information [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	4,161,452	3,846,682
Canada Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	126,372	85,405
Canada Segment Reporting Information [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	4,287,824	3,932,087
EMEA Traditional Segment Reporting Information [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	3,099,495	2,559,124
EMEA Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	5,274,993	3,876,131
EMEA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	8,374,488	6,435,255
Asia Pacific Traditional Segment Reporting Information [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	4,915,442	3,968,081
Asia Pacific Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,198,585	676,281
Asia Pacific [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	6,114,027	4,644,362
Corporate Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 7,175,850	$ 6,233,244

Short-Duration Contracts (Claim

Short-Duration Contracts (Claims Development) (Details) - Life Insurance Product Line [Member] - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net		$ 1,527,827
Asia Pacific [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	1,138,783
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	1,725,445
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	[1]	144,984
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	[1]	731,646
Americas [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	1,894,362
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	2,481,669
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	[1]	208,874
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	[1]	796,181
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Asia Pacific [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	287,941	$ 269,808	$ 247,028	$ 205,303	$ 149,912	$ 54,638
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	336,901	325,992	317,536	313,862	309,090	230,295
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		13,196
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Americas [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	263,565	258,297	252,018	243,890	222,139	109,323
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	297,688	299,098	298,262	297,037	309,119	$ 322,579
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		24
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Asia Pacific [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	289,472	261,359	231,919	159,799	55,175
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	347,865	333,639	336,531	346,886	324,334
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		21,310
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Americas [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	292,067	285,817	277,130	248,828	114,457
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	336,436	336,552	338,977	332,907	$ 349,262
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		164
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Asia Pacific [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	228,405	196,570	150,295	38,241
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	300,025	294,049	332,718	306,919
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		27,113
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Americas [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	349,078	337,081	304,578	128,813
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	397,151	396,383	411,373	$ 407,953
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		1,597
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Asia Pacific [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	185,393	131,364	54,241
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	277,166	284,871	308,517
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		44,713
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Americas [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	407,282	360,658	146,196
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	465,167	460,917	$ 459,524
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		3,809
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Asia Pacific [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	108,310	42,440
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	228,342	252,197
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		62,959
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Americas [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	392,517	184,940
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	499,785	$ 500,843
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		23,149
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Asia Pacific [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	39,262
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	235,146
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		140,159
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Americas [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	[1]	189,853
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	[1]	485,442
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		$ 200,109
[1]	2012-2016 Unaudited.

Short-Duration Contracts (Recon

Short-Duration Contracts (Reconciliation of Claims Development to Liability) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Discounted Liabilities, Aggregate Discount	$ (128,391)
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Other Reconciling Item	2,019,290
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Aggregate Reconciling Items	25,336,025
Liability for Claims and Claims Adjustment Expense	27,355,315
Canada Segment Reporting Information [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Other Reconciling Item	150,248
EMEA [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Other Reconciling Item	346,916
Corporate And Other Segment Reporting Information [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Other Reconciling Item	122,690
Life Insurance Product Line [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	1,527,827
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	17,940
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	(146,331)
Life Insurance Product Line [Member] | Americas [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	796,181	[1]
Life Insurance Product Line [Member] | Asia Pacific [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	$ 731,646	[1]
[1]	2012-2016 Unaudited.

Short-Duration Contracts Short-

Short-Duration Contracts Short-Duration Contracts (Schedule of Historical Claims Duration) (Details) - Life Insurance Product Line [Member]	Dec. 31, 2017
Americas [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	35.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	41.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	8.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	2.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	2.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	1.80%
Asia Pacific [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	16.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	30.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	18.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	10.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	7.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	5.40%

Earnings Per Share (Schedule of

Earnings Per Share (Schedule of Earnings Per Share Basic and Diluted) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Income (Loss) Attributable to Parent	$ 1,216,888	$ 227,591	$ 232,190	$ 145,512	$ 190,149	$ 198,719	$ 236,103	$ 76,472	$ 1,822,181	$ 701,443	$ 502,166
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted Average Number of Shares Outstanding, Basic									64,427	64,274	66,553
Equivalent shares from outstanding stock options									1,326	715	739
Weighted Average Number of Shares Outstanding, Diluted									65,753	64,989	67,292
Earnings per share
Earnings Per Share, Basic (in dollars per share)	$ 18.89	$ 3.53	$ 3.60	$ 2.26	$ 2.96	$ 3.10	$ 3.68	$ 1.18	$ 28.28	$ 10.91	$ 7.55
Earnings Per Share, Diluted (in dollars per share)	$ 18.49	$ 3.47	$ 3.54	$ 2.22	$ 2.92	$ 3.07	$ 3.64	$ 1.17	$ 27.71	$ 10.79	$ 7.46

Earnings Per Share Earnings Per

Earnings Per Share Earnings Per Share (Narrative) (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.2	0	0.3
Contingently Issuable Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.3	0.4	0.4

Equity Equity (Common Stock Cha

Equity Equity (Common Stock Changes in Number of Shares Issued, Held in Treasury and Oustanding) (Details) - shares		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Common Stock, Shares, Issued		79,137,758	79,137,758
Treasury Stock, Shares, Acquired		(208,680)	(1,356,892)	(4,145,440)
Common Stock Issuable [Member]
Class of Stock [Line Items]
Common Stock, Shares, Issued		79,137,758	79,137,758	79,137,758	79,137,758
Stock Based Compensation Shares	[1]	0	0	0
Treasury Stock, Shares, Acquired		0	0	0
Common Stock Held In Treasury [Member]
Class of Stock [Line Items]
Common Stock, Shares, Issued		14,685,663	14,835,256	13,933,232	10,364,797
Stock Based Compensation Shares	[1]	(358,273)	(454,868)	(577,005)
Treasury Stock, Shares, Acquired		(208,680)	(1,356,892)	(4,145,440)
Common Stock Outstanding [Member]
Class of Stock [Line Items]
Common Stock, Shares, Issued		64,452,095	64,302,502	65,204,526	68,772,961
Stock Based Compensation Shares	[1]	358,273	454,868	577,005
Treasury Stock, Shares, Acquired		(208,680)	(1,356,892)	(4,145,440)
[1]	Represents net shares issued from treasury pursuant to the Company’s stock-based compensation programs.

Equity (Components of Other Com

Equity (Components of Other Comprehensive Income) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax		$ 74,926	$ 39,925	$ (342,539)
Other Comprehensive Income (Loss), Foreign Currency Translation Gain (Loss) Arising During Period, Tax		25,369	(24,663)	17,129
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax		100,295	15,262	(325,410)
Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Foreign Currency Swap, Before Reclassification and Tax		(47,953)	(10,234)	96,019
Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Foreign Currency Swap Tax		16,784	3,582	(33,607)
Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Foreign Currency Swap Net Of Tax		(31,169)	(6,652)	62,412
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax		26,973	29,691	(246,520)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax		42,153	(21,081)	(16,478)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax		69,126	8,610	(262,998)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	[1]	1,029,591	641,606	(1,084,732)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	[1]	(313,729)	(180,448)	359,407
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	[1]	715,862	461,158	(725,325)
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, before Tax	[1]	25,039	65,798	(55,767)
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Tax	[1]	(7,011)	(23,029)	19,518
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	[1]	18,028	42,769	(36,249)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Reclassification Adjustments and Tax	[1]	1,004,552	575,808	(1,028,965)
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax	[1]	(306,718)	(157,419)	339,889
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	[1]	697,834	418,389	(689,076)
Other than Temporary Impairment Loss, Investments, Portion in Other Comprehensive Loss, before Tax, Portion Attributable to Parent, Available-for-sale Securities		375	(1,457)
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, Tax, Portion Attributable to Parent, Available-for-sale Securities		(131)	(510)
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, Net of Tax, Portion Attributable to Parent, Available-for-sale Securities		244	947
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		11,717	444	337
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, Tax		(4,095)	(149)	(107)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax		7,622	295	230
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		(10,587)	4,427	4,618
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax		3,691	(1,623)	(1,619)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		(6,896)	2,804	2,999
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax		1,130	4,871	4,955
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax		(404)	(1,772)	(1,726)
Defined benefit pension and postretirement plan adjustments		726	3,099	3,229
Other Comprehensive Income (Loss), before Tax		1,033,030	611,827	(1,270,530)
Other Comprehensive Income (Loss), Tax		(265,100)	(180,782)	321,685
Other Comprehensive Income (Loss), Net of Tax		$ 767,930	$ 431,045	$ (948,845)
[1]	Includes cash flow hedges. See Note 5 for additional information on cash flow hedges.

Equity (Components of Net Unrea

Equity (Components of Net Unrealized Appreciation Depreciation of Balances Carried at Fair Value) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Comprehensive Income Net Of Tax [Line Items]
Fixed maturity securities available-for-sale		$ 38,150,820	$ 32,093,625
Other invested assets		1,605,484	1,591,940
Deferred policy acquisition costs		3,239,824	3,338,605	$ 3,392,437	$ 3,342,575
Accumulated Other Comprehensive Income Loss Change In Component During Period		1,004,927	577,265	(1,028,965)
Change In Net Unrealized Appreciation Depreciation [Member]
Comprehensive Income Net Of Tax [Line Items]
Fixed maturity securities available-for-sale		987,570	561,906	(1,055,458)
Other invested assets	[1]	25,577	18,900	8,983
Effect On Unrealized Appreciation Depreciation [Member]
Comprehensive Income Net Of Tax [Line Items]
Deferred policy acquisition costs		$ (8,220)	$ (3,541)	$ 17,510
[1]	Includes cash flow hedges. See Note 5 for additional information on cash flow hedges.

Equity (Balance of and Changes

Equity (Balance of and Changes in Each Component of AOCI) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income Loss Net Of Tax [Roll Forward]
Balance, beginning of year		$ 1,139,329	$ 708,284	$ 1,657,129
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax		1,062,087	675,627	(1,349,528)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		(29,057)	(63,800)	78,998
Other Comprehensive Income (Loss), Tax		(265,100)	(180,782)	321,685
Balance, end of year		2,063,631	1,139,329	708,284
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Roll Forward]
Balance, beginning of year		(172,541)	(181,151)	81,847
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax		26,973	29,691	(246,520)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		0	0	0
Other Comprehensive Income (Loss), Tax		42,153	(21,081)	(16,478)
Balance, end of year		(86,350)	(172,541)	(181,151)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Roll Forward]
Balance, beginning of year	[1]	1,355,033	935,697	1,624,773
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	[1]	1,039,387	646,887	(1,101,760)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	34,460	69,622	(72,795)
Other Comprehensive Income (Loss), Tax	[1]	(306,849)	(157,929)	339,889
Balance, end of year	[1]	2,200,661	1,355,033	935,697
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Roll Forward]
Balance, beginning of year		(43,163)	(46,262)	(49,491)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax		(4,273)	(951)	(1,248)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		(5,403)	(5,822)	(6,203)
Other Comprehensive Income (Loss), Tax		(404)	(1,772)	(1,726)
Balance, end of year		(50,680)	$ (43,163)	$ (46,262)
Accounting Standards Update 2018 02 [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		17,723
Accounting Standards Update 2018 02 [Member] | Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		17,065
Accounting Standards Update 2018 02 [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		147,550
Accounting Standards Update 2018 02 [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		(8,243)
Accounting Standards Update 2018 02 [Member] | AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income Loss Net Of Tax [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		$ 156,372
[1]	Includes cash flow hedges of $2,619, $(2,496) and $(29,397) as of December 31, 2017, 2016 and 2015, respectively. See Note 5 for additional information on cash flow hedges.

Equity Equity (Balance of and C

Equity Equity (Balance of and Changes in Each Component of AOCI) (Footnote) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	$ 2,619	$ (2,496)	$ (29,397)	$ (31,591)

Equity (Schedule of Reclassific

Equity (Schedule of Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other investment related gains (losses), net										$ 210,519	$ 132,926	$ (107,370)
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities										0	(74)	0
Investment income, net of related expenses										2,154,651	1,911,886	1,734,495
Deferred Policy Acquisition Cost, Amortization Expense, Unrealized Investment Gains (Losses)										8,220	3,541	(17,510)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax										(11,717)	(444)	(337)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax										10,587	(4,427)	(4,618)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest		$ 255,494	$ 340,162	$ 339,315	$ 207,844	$ 295,543	$ 287,600	$ 353,223	$ 107,580	1,142,815	1,043,946	744,795
Income Tax Expense (Benefit)										679,366	(342,503)	(242,629)
Net Income (Loss) Attributable to Parent		$ 1,216,888	$ 227,591	$ 232,190	$ 145,512	$ 190,149	$ 198,719	$ 236,103	$ 76,472	1,822,181	701,443	$ 502,166
Amortization Of Unrealized Pension And Postretirement Benefits [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	[1]									971	(328)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	[1]									(6,374)	(6,150)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest										(5,403)	(5,822)
Income Tax Expense (Benefit)										1,891	2,038
Net Income (Loss) Attributable to Parent										(3,512)	(3,784)
Unrealized Appreciation Depreciation Of Investments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other investment related gains (losses), net										25,039	65,798
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities										0	74
Deferred Policy Acquisition Cost, Amortization Expense, Unrealized Investment Gains (Losses)	[2]									8,220	3,541
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest										34,460	69,622
Income Tax Expense (Benefit)										(10,308)	(17,672)
Net Income (Loss) Attributable to Parent										24,152	51,950
Amounts Reclassified From AOCI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income (Loss) Attributable to Parent										20,640	48,166
Interest Rate Options [Member] | Unrealized Gains Losses On Available For Sale Securities [Member] | Unrealized Appreciation Depreciation Of Investments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	[3]									(79)	0
Currency Swap [Member] | Unrealized Gains Losses On Available For Sale Securities [Member] | Unrealized Appreciation Depreciation Of Investments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	[3]									380	510
Forward Contracts [Member] | Unrealized Gains Losses On Available For Sale Securities [Member] | Unrealized Appreciation Depreciation Of Investments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	[3]									$ 900	$ (301)
[1]	See Note 10 for information on employee benefit plans.
[2]	See Note 8 for information on deferred policy acquisition costs.
[3]	See Note 5 for information on cash flow hedges.

Equity (Narrative) (Details)

Equity (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Stock Repurchase Program, Authorized Amount	$ 400,000	$ 400,000	$ 450,000
Treasury Stock, Shares, Acquired	208,680	1,356,892	4,145,440
Treasury Stock Value Acquired Cost Method Repurchase Agreement	$ 26,900	$ 116,500	$ 375,300
Treasury Stock, Value, Acquired, Cost Method	$ 43,508	$ 122,916	$ 384,519

Equity Based Compensation (Disc

Equity Based Compensation (Disclosure of Share-based Compensation Arrangements by Share-based Payment Award) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options, Grants in Period, Weighted Average Exercise Price	$ 129.72	$ 93.53	$ 91.65
Options, Outstanding, Intrinsic Value	$ 186.5
Options, Exercisable, Intrinsic Value	$ 152.9
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, Number, Beginning Balance	2,573,223,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	171,388,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	(430,429,000)
Forfeited	(4,413,000)
Outstanding, Number, Ending Balance	2,309,769,000	2,573,223,000
Options exercisable	1,700,629,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options, Outstanding, Weighted Average Exercise Price, Beginning of Period	$ 68.70
Options, Grants in Period, Weighted Average Exercise Price	129.72
Exercised / Lapsed	58.07
Forfeited	87.15
Options, Outstanding, Weighted Average Exercise Price, End of Period	75.17	$ 68.70
Options exercisable	$ 66.04

Equity Based Compensation (D158

Equity Based Compensation (Disclosure of Share-based Compensation Shares Authorized under Stock Option Plans by Exercise Price Range) (Details)	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding | shares	2,309,769,000
Options Outstanding, Weighted-Average Remaining Contractual Life	5 years 9 months
Options Outstanding, Weighted Average Exercise Price	$ 75.17
Options Exercisable | shares	1,700,629,000
Options Exercisable, Weighted-Average Exercise Price	$ 66.04
$0.00 - $49.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding | shares	245,264,000
Options Outstanding, Weighted-Average Remaining Contractual Life	1 year 8 months
Options Outstanding, Weighted Average Exercise Price	$ 40.54
Options Exercisable | shares	245,264,000
Options Exercisable, Weighted-Average Exercise Price	$ 40.54
Exercise Price Range, Lower Range Limit	25
Exercise Price Range, Upper Range Limit	$ 44.99
$50.00 - $59.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding | shares	902,246,000
Options Outstanding, Weighted-Average Remaining Contractual Life	4 years 5 months
Options Outstanding, Weighted Average Exercise Price	$ 58.23
Options Exercisable | shares	902,246,000
Options Exercisable, Weighted-Average Exercise Price	$ 58.23
$60.00 - $69.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding | shares	839,000
Options Outstanding, Weighted-Average Remaining Contractual Life	5 years 2 months
Options Outstanding, Weighted Average Exercise Price	$ 60.24
Options Exercisable | shares	839,000
Options Exercisable, Weighted-Average Exercise Price	$ 60.24
Exercise Price Range, Lower Range Limit	45
Exercise Price Range, Upper Range Limit	$ 54.99
$70.00 - $79.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding | shares	190,137,000
Options Outstanding, Weighted-Average Remaining Contractual Life	6 years 2 months
Options Outstanding, Weighted Average Exercise Price	$ 78.48
Options Exercisable | shares	190,137,000
Options Exercisable, Weighted-Average Exercise Price	$ 78.48
Exercise Price Range, Lower Range Limit	$ 55
$90.00 plus [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding | shares	971,283,000
Options Outstanding, Weighted-Average Remaining Contractual Life	8 years 1 month
Options Outstanding, Weighted Average Exercise Price	$ 99.02
Options Exercisable | shares	362,143,000
Options Exercisable, Weighted-Average Exercise Price	$ 96.22

Equity Based Compensation (Weig

Equity Based Compensation (Weighted Average Assumptions) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	1.26%	1.58%	1.47%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	2.32%	1.69%	2.04%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	22.80%	28.10%	35.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	7 years	7 years	7 years
Options, Grants in Period, Weighted Average Exercise Price	$ 129.72	$ 93.53	$ 91.65
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 31.57	$ 24.52	$ 30.50

Equity Based Compensation (Summ

Equity Based Compensation (Summary of Performance Contingent Unit Activity) (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Number, Beginning Balance	585,971
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	115,176
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	137,083	94,436
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	100,805
Outstanding, Number, Ending Balance	463,259	585,971
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Number, Beginning Balance	96,628
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	22,971
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	38,843
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	3,398
Outstanding, Number, Ending Balance	77,358	96,628

Equity Based Compensation (Narr

Equity Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, Exercises in Period, Total Intrinsic Value	$ 42.1	$ 41.4	$ 26.2
Performance Contingent Unit Share Payout	0.75	0.400
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	1 year 6 months
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 26.3
Performance Contingent Units Measurement Period	3 years
Allocated Share-based Compensation Expense	$ 22.3	$ 33.1	$ 16
Options, Grants in Period, Weighted Average Exercise Price	$ 129.72	$ 93.53	$ 91.65
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	430,429,000
Expiration Period	10 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	171,388,000
Options, Grants in Period, Weighted Average Exercise Price	$ 129.72
Flexible Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Of Shares Available For Grant	14,960,077
Flexible Stock Plan For Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Of Shares Available For Grant	412,500
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	137,083	94,436
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	115,176
Options, Grants in Period, Weighted Average Exercise Price	$ 129.72
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	38,843
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	22,971
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	1 year
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	5 years

Quarterly Results of Operati162

Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 3,232,443	$ 3,145,310	$ 3,129,276	$ 3,008,740	$ 3,069,298	$ 2,900,577	$ 3,039,068	$ 2,512,568	$ 12,515,769	$ 11,521,511	$ 10,418,178
Total benefits and expenses	2,976,949	2,805,148	2,789,961	2,800,896	2,773,755	2,612,977	2,685,845	2,404,988	11,372,954	10,477,565	9,673,383
Income before income taxes	255,494	340,162	339,315	207,844	295,543	287,600	353,223	107,580	1,142,815	1,043,946	744,795
Net Income (Loss) Attributable to Parent	$ 1,216,888	$ 227,591	$ 232,190	$ 145,512	$ 190,149	$ 198,719	$ 236,103	$ 76,472	$ 1,822,181	$ 701,443	$ 502,166
Basic earnings per share:
Earnings Per Share, Basic (in dollars per share)	$ 18.89	$ 3.53	$ 3.60	$ 2.26	$ 2.96	$ 3.10	$ 3.68	$ 1.18	$ 28.28	$ 10.91	$ 7.55
Earnings Per Share, Diluted (in dollars per share)	$ 18.49	$ 3.47	$ 3.54	$ 2.22	$ 2.92	$ 3.07	$ 3.64	$ 1.17	$ 27.71	$ 10.79	$ 7.46

Summary of Investments Other163

Summary of Investments Other Than Investments in Related Parties (Details) $ in Millions	Dec. 31, 2017USD ($)
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	$ 48,824
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	51,691	[1]
Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	35,281
Summary of Investments, Other than Investments in Related Parties, Fair Value	38,151
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	38,151	[1]
US Treasury and Government [Member] | Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	1,953
Summary of Investments, Other than Investments in Related Parties, Fair Value	1,944
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,944	[1]
US States and Political Subdivisions Debt Securities [Member] | Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	648
Summary of Investments, Other than Investments in Related Parties, Fair Value	703
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	703	[1]
Foreign Government Debt [Member] | Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	6,098	[2]
Summary of Investments, Other than Investments in Related Parties, Fair Value	7,621	[2]
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	7,621	[1],[2]
Public Utility, Bonds [Member] | Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	2,454
Summary of Investments, Other than Investments in Related Parties, Fair Value	2,649
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	2,649	[1]
Asset-backed Securities [Member] | Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	4,615
Summary of Investments, Other than Investments in Related Parties, Fair Value	4,672
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	4,672	[1]
All Other Corporate Bonds [Member] | Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	19,513
Summary of Investments, Other than Investments in Related Parties, Fair Value	20,562
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	20,562	[1]
Nonredeemable Preferred Stock [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	42
Summary of Investments, Other than Investments in Related Parties, Fair Value	40
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	40	[1]
Other Equity Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	61
Summary of Investments, Other than Investments in Related Parties, Fair Value	60
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	60	[1]
Equity Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	103
Summary of Investments, Other than Investments in Related Parties, Fair Value	100
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	100	[1]
Mortgage Loans on Real Estate [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	4,401
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	4,401	[1]
Policy Loans [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	1,358
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	1,358	[1]
Funds Withheld At Interest [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	6,083
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	6,083	[1]
Short-term Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	93
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	93	[1]
Other Invested Assets [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Summary of Investments, Other than Investments in Related Parties, Cost	1,505
Summary of Investments, Other than Investments in Related Parties, Carrying Amount	$ 1,505	[1]
[1]	Fixed maturity securities are classified as available-for-sale and carried at fair value.
[2]	Includes fixed maturities directly issued by foreign governments, supranational and foreign government-sponsored enterprises.

Condensed Financial Informat164

Condensed Financial Information of The Registrant (Details) - USD ($)		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2006
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													$ 2,808,770,000	$ 3,110,853,000
Debt Issuance Cost													(20,405,000)	(22,218,000)
Long-term debt													2,788,365,000	3,088,635,000
Assets
Fixed maturity securities available-for-sale													38,150,820,000	32,093,625,000
Short-term investments													93,304,000	76,710,000
Cash and cash equivalents		$ 1,303,524,000			$ 1,200,718,000	$ 1,200,718,000			$ 1,525,275,000	$ 1,200,718,000	$ 1,525,275,000	$ 1,645,669,000	1,303,524,000	1,200,718,000	$ 1,525,275,000	$ 1,645,669,000
Other assets													767,088,000	755,338,000
Total assets													60,514,818,000	53,097,879,000
Liabilities and Stockholders’ Equity
Other liabilities													1,102,975,000	1,041,880,000
Total stockholders equity													9,569,535,000	7,093,082,000	6,135,381,000	7,023,452,000
Total liabilities and stockholders’ equity													60,514,818,000	53,097,879,000
CONSOLIDATED STATEMENTS OF INCOME
Total investment related gains (losses), net										167,880,000	94,195,000	(164,750,000)
Income Tax Expense (Benefit)										(679,366,000)	342,503,000	242,629,000
Net Income (Loss) Attributable to Parent		1,216,888,000	$ 227,591,000	$ 232,190,000	145,512,000	190,149,000	$ 198,719,000	$ 236,103,000	76,472,000	1,822,181,000	701,443,000	502,166,000
Other Comprehensive Income (Loss), Net of Tax										767,930,000	431,045,000	(948,845,000)
Total comprehensive income (loss)										2,590,111,000	1,132,488,000	(446,679,000)
Debt Disclosure [Abstract]
Debt Instrument, Face Amount																	$ 850,000,000
Cash flows from operating activities
Net Income (Loss) Attributable to Parent		1,216,888,000	$ 227,591,000	$ 232,190,000	145,512,000	190,149,000	$ 198,719,000	$ 236,103,000	76,472,000	1,822,181,000	701,443,000	502,166,000
Other, net										24,216,000	117,949,000	(49,564,000)
Net cash provided by operating activities										1,982,308,000	1,465,718,000	2,088,615,000
Cash flows from investing activities
Sales of fixed maturity securities available-for-sale										7,308,608,000	4,584,828,000	5,461,687,000
Payments to Acquire Businesses, Net of Cash Acquired										0	0	(145,235,000)
Payments for (Proceeds from) Short-term Investments										52,302,000	465,628,000	(470,002,000)
Payments for (Proceeds from) Other Investing Activities										(121,206,000)	(97,790,000)	91,960,000
Net cash used in investing activities										(1,607,573,000)	(2,825,726,000)	(1,431,741,000)
Cash flows from financing activities
Dividends to stockholders										(117,291,000)	(100,371,000)	(93,381,000)
Purchases of treasury stock										(43,508,000)	(122,916,000)	(384,519,000)
Excess tax benefits from share-based payment arrangement cash flow										0	162,000	2,963,000
Exercise of stock options, net										7,292,000	15,321,000	11,151,000
Maturities of Senior Debt										302,582,000	2,479,000	2,380,000
Proceeds from affiliated long-term debt issuance										0	(799,984,000)	0
Payments Of Debt Issuance Costs										0	(8,766,000)	(4,748,000)
Net cash used in financing activities										(324,622,000)	1,055,389,000	(708,282,000)
Change in cash and cash equivalents										102,806,000	(324,557,000)	(120,394,000)
Cash and cash equivalents, beginning of period					1,200,718,000				1,525,275,000	1,200,718,000	1,525,275,000	1,645,669,000
Cash and cash equivalents, end of period		1,303,524,000				1,200,718,000				1,303,524,000	1,200,718,000	1,525,275,000
Supplementary information:
Interest paid										173,471,000	156,727,000	148,124,000
Income taxes paid, net of refunds										37,098,000	61,085,000	41,577,000
Cash Acquired from Acquisition										0	0	69,823,000
Parent Company [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													2,796,913,000	3,096,413,000
Debt Issuance Cost													(21,334,000)	(23,164,000)
Long-term debt	[1]												2,775,579,000	3,073,249,000
Assets
Fixed maturity securities available-for-sale													710,303,000	1,154,559,000
Short-term investments													54,517,000	245,478,000
Cash and cash equivalents		15,176,000			43,718,000	43,718,000			39,452,000	43,718,000	39,452,000	48,819,000	15,176,000	43,718,000	$ 39,452,000	$ 48,819,000
Investments In Subsidiary													12,043,911,000	9,209,700,000
Loans and Leases Receivable, Related Parties													1,010,000,000	1,050,000,000
Other assets													234,707,000	258,379,000
Total assets													14,068,614,000	11,961,834,000
Liabilities and Stockholders’ Equity
Long-term debt - affiliated	[2]												500,000,000	500,000,000
Other liabilities													1,223,500,000	1,295,503,000
Total stockholders equity													9,569,535,000	7,093,082,000
Total liabilities and stockholders’ equity													14,068,614,000	11,961,834,000
CONSOLIDATED STATEMENTS OF INCOME
Interest and Dividend Income, Operating	[3]									131,067,000	602,830,000	321,645,000
Total investment related gains (losses), net										(5,187,000)	203,000	(324,000)
Operating Expenses										(20,517,000)	(20,742,000)	(13,652,000)
Interest and Debt Expense										(177,417,000)	(168,924,000)	(176,364,000)
Income (loss) before income tax and undistributed earnings of subsidiaries										(72,054,000)	413,367,000	131,305,000
Income Tax Expense (Benefit)										65,882,000	(23,911,000)	(19,465,000)
Net income (loss) before undistributed earnings of subsidiaries										(137,936,000)	437,278,000	150,770,000
Equity In Undistributed Earnings Of Subsidiaries										1,960,117,000	264,165,000	351,396,000
Net Income (Loss) Attributable to Parent										1,822,181,000	701,443,000	502,166,000
Other Comprehensive Income (Loss), Net of Tax										(7,672,000)	5,531,000	44,073,000
Total comprehensive income (loss)										1,814,509,000	706,974,000	546,239,000
Debt Disclosure [Abstract]
Proceeds from Dividends Received										0	478,602,000	196,445,000
Long-term Debt													500,000,000	500,000,000
Cash flows from operating activities
Net Income (Loss) Attributable to Parent										1,822,181,000	701,443,000	502,166,000
Equity Net Earnings Subsidiaries										(1,960,117,000)	(264,165,000)	(351,396,000)
Other, net										57,677,000	(63,795,000)	486,159,000
Net cash provided by operating activities										(80,259,000)	373,483,000	636,929,000
Cash flows from investing activities
Sales of fixed maturity securities available-for-sale										514,508,000	228,383,000	100,734,000
Purchases of fixed maturity securities available-for-sale										(75,000,000)	(984,397,000)	(52,698,000)
Purchases Of Subsidiary Debt Securities										40,000,000	20,000,000	(10,000,000)
Payments to Acquire Businesses, Net of Cash Acquired										0	0	(3,701,000)
Payments for (Proceeds from) Short-term Investments										0	102,508,000	(102,508,000)
Payments for (Proceeds from) Other Investing Activities										125,506,000	(109,914,000)	(7,542,000)
Capital Contributions To Subsidiaries										(62,500,000)	(314,142,000)	(103,832,000)
Net cash used in investing activities										542,514,000	(1,057,562,000)	(179,547,000)
Cash flows from financing activities
Dividends to stockholders										(117,291,000)	(100,371,000)	(93,381,000)
Purchases of treasury stock										(43,508,000)	(122,916,000)	(384,519,000)
Exercise of stock options, net										7,292,000	15,321,000	11,151,000
Net Change In Cash Collateral For Loaned Securities										(37,290,000)	105,093,000	0
Maturities of Senior Debt										(300,000,000)	0	0
Proceeds from affiliated long-term debt issuance										0	(799,984,000)	0
Payments Of Debt Issuance Costs										0	(8,766,000)	0
Net cash used in financing activities										(490,797,000)	688,345,000	(466,749,000)
Change in cash and cash equivalents										(28,542,000)	4,266,000	(9,367,000)
Cash and cash equivalents, beginning of period					$ 43,718,000				$ 39,452,000	43,718,000	39,452,000	48,819,000
Cash and cash equivalents, end of period		$ 15,176,000				$ 43,718,000				15,176,000	43,718,000	39,452,000
Supplementary information:
Interest paid										185,554,000	169,860,000	165,775,000
Income taxes paid, net of refunds										8,248,000	1,500,000	(120,680,000)
Cash Acquired from Acquisition										0	$ 0	$ 529,000
Senior Notes Due 2017 [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													0	299,945,000
Debt Disclosure [Abstract]
Debt Instrument, Face Amount													$ 300,000,000
Debt Instrument, Interest Rate, Stated Percentage													5.625%
Senior Notes Due 2017 [Member] | Parent Company [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													$ 0	299,945,000
Debt Disclosure [Abstract]
Repayments of Long-term Debt										300,000,000
Senior Notes Due 2019 [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													399,873,000	399,805,000
Debt Disclosure [Abstract]
Debt Instrument, Face Amount													$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage													6.45%
Senior Notes Due 2019 [Member] | Parent Company [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													$ 399,873,000	399,805,000
Debt Disclosure [Abstract]
Repayments of Long-term Debt										$ 400,000,000
Senior Notes Due 2021 [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													399,245,000	399,025,000
Debt Disclosure [Abstract]
Debt Instrument, Face Amount													$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage													5.00%
Senior Notes Due 2021 [Member] | Parent Company [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													$ 399,245,000	399,025,000
Senior Notes Due 2023 [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													399,138,000	398,986,000
Debt Disclosure [Abstract]
Debt Instrument, Face Amount													$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage													4.70%
Senior Notes Due 2023 [Member] | Parent Company [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													$ 399,138,000	398,986,000
Senior Notes Due 2026 [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													399,987,000	399,985,000
Debt Issuance Cost													(8,800,000)
Debt Disclosure [Abstract]
Debt Instrument, Face Amount													$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage													3.95%
Senior Notes Due 2026 [Member] | Parent Company [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													$ 399,987,000	399,985,000
Subordinated Debentures Due 2042 [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													400,000,000	400,000,000
Debt Disclosure [Abstract]
Debt Instrument, Face Amount													$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage													6.20%
Subordinated Debentures Due 2042 [Member] | Parent Company [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													$ 400,000,000	400,000,000
Subordinated Debentures Due 2056 [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													400,000,000	400,000,000
Debt Disclosure [Abstract]
Debt Instrument, Face Amount													$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage													5.75%
Subordinated Debentures Due 2056 [Member] | Parent Company [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													$ 400,000,000	400,000,000
Junior Subordinated Debentures Due 2065 [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													318,740,000	318,737,000
Debt Disclosure [Abstract]
Debt Instrument, Face Amount													400,000,000
Junior Subordinated Debentures Due 2065 [Member] | Parent Company [Member]
Supplemental Condensed Financial Information Of The Registrant [Line Items]
Long-term Debt, Gross													$ 398,670,000	$ 398,667,000
[1]	Long-term debt - unaffiliated consists of the following: 2017 2016$300 million 5.625% Senior Notes due 2017 $— $299,945$400 million 6.45% Senior Notes due 2019 399,873 399,805$400 million 5.00% Senior Notes due 2021 399,245 399,025$400 million 4.70% Senior Notes due 2023 399,138 398,986$400 million 3.95% Senior Notes due 2026 399,987 399,985$400 million 6.20% Subordinated Debentures due 2042 400,000 400,000$400 million 5.75% Subordinated Debentures due 2056 400,000 400,000$400 million Variable Rate Junior Subordinated Debentures due 2065 398,670 398,667Subtotal 2,796,913 3,096,413Unamortized debt issue costs (21,334) (23,164)Total $2,775,579 $3,073,249Repayments of long-term debt—unaffiliated due over the next five years total $400,000 in 2019 and $400,000 in 2021.
[2]	Long-term debt—affiliated in 2017 and 2016 and consists of $500,000 of subordinated debt issued to various operating subsidiaries.
[3]	Interest/Dividend income includes $478,602 and $196,445 of cash dividends received from consolidated subsidiaries in 2016 and 2015, respectively. In 2017 there were no cash dividends received from consolidated subsidiaries.

Supplementary Insurance Info165

Supplementary Insurance Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	$ 3,239,824	$ 3,338,605
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	38,590,883	33,610,927
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	4,992,074	4,263,026
Supplementary Insurance Information, Premium Revenue	9,841,130	9,248,871	$ 8,570,741
Supplementary Insurance Information, Net Investment Income	2,154,651	1,911,886	1,734,495
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	9,020,957	8,358,066	7,826,346
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	502,866	381,192	229,876
Supplementary Insurance Information, Other Operating Expense	1,849,131	1,738,307	1,617,161
US Traditional Segment Reporting Information [Member]
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	1,818,572	1,818,211
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	11,343,921	10,990,560
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	1,814,018	1,659,473
Supplementary Insurance Information, Premium Revenue	5,356,321	5,249,571	4,806,706
Supplementary Insurance Information, Net Investment Income	728,073	699,833	636,779
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	4,842,412	4,717,850	4,444,196
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	191,725	177,255	131,439
Supplementary Insurance Information, Other Operating Expense	692,600	698,762	653,620
US Non-Traditional Segment Reporting Information [Member]
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	405,623	582,031
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	15,127,529	13,074,231
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	17,876	20,352
Supplementary Insurance Information, Premium Revenue	23,683	24,349	22,177
Supplementary Insurance Information, Net Investment Income	778,473	631,097	566,180
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	458,368	333,107	310,464
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	185,280	133,501	40,416
Supplementary Insurance Information, Other Operating Expense	105,146	90,458	85,022
Canada Traditional Segment Reporting Information [Member]
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	212,345	201,149
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	3,041,790	2,713,510
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	206,655	200,246
Supplementary Insurance Information, Premium Revenue	901,976	928,642	838,894
Supplementary Insurance Information, Net Investment Income	189,018	178,927	182,621
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	757,912	707,428	670,477
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	12,426	10,621	11,299
Supplementary Insurance Information, Other Operating Expense	212,964	265,250	217,061
Canada Non-Traditional Segment Reporting Information [Member]
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	0	0
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	27,908	29,531
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	1,040	4,599
Supplementary Insurance Information, Premium Revenue	38,229	38,701	37,969
Supplementary Insurance Information, Net Investment Income	5,115	2,692	1,436
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	29,639	36,275	29,251
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	0	0	0
Supplementary Insurance Information, Other Operating Expense	2,656	2,718	1,881
EMEA Traditional Segment Reporting Information [Member]
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	229,150	206,837
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	1,075,786	913,351
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	882,744	740,218
Supplementary Insurance Information, Premium Revenue	1,301,640	1,140,062	1,121,540
Supplementary Insurance Information, Net Investment Income	55,511	50,301	51,370
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	1,096,211	999,005	979,225
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	20,570	33,795	39,164
Supplementary Insurance Information, Other Operating Expense	174,808	132,290	123,943
EMEA Non-Traditional Segment Reporting Information [Member]
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	0	0
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	4,741,983	3,457,196
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	38,044	46,761
Supplementary Insurance Information, Premium Revenue	163,720	180,271	171,830
Supplementary Insurance Information, Net Investment Income	123,258	125,282	73,432
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	153,874	178,014	161,917
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	0	0	0
Supplementary Insurance Information, Other Operating Expense	33,683	24,497	16,304
Asia Pacific Traditional Segment Reporting Information [Member]
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	552,947	512,123
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	1,611,633	1,288,642
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	2,017,920	1,563,707
Supplementary Insurance Information, Premium Revenue	2,053,029	1,681,505	1,551,586
Supplementary Insurance Information, Net Investment Income	91,675	83,049	80,549
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	1,635,728	1,345,951	1,208,984
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	91,477	24,597	7,373
Supplementary Insurance Information, Other Operating Expense	334,695	286,674	316,346
Asia Pacific Non-Traditional Segment Reporting Information [Member]
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	21,187	18,254
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	1,118,012	641,614
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	6,885	19,643
Supplementary Insurance Information, Premium Revenue	2,419	5,428	19,474
Supplementary Insurance Information, Net Investment Income	34,529	23,648	18,678
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	40,467	37,976	20,766
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	1,388	1,423	185
Supplementary Insurance Information, Other Operating Expense	18,790	19,920	16,011
Corporate And Other Segment Reporting Information [Member]
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Deferred Policy Acquisition Costs	0	0
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves	502,321	502,292
Supplementary Insurance Information, Other Policy Claims and Benefits Payable	6,892	8,027
Supplementary Insurance Information, Premium Revenue	113	342	565
Supplementary Insurance Information, Net Investment Income	148,999	117,057	123,450
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	6,346	2,460	1,066
Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Costs	0	0	0
Supplementary Insurance Information, Other Operating Expense	$ 273,789	$ 217,738	$ 186,973

Supplemental Schedule of Rei166

Supplemental Schedule of Reinsurance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums, Life Insurance in Force	$ 1,462,000	$ 1,576,000	$ 1,686,000
Ceded Premiums, Life Insurance in Force	205,529,000	214,727,000	222,388,000
Assumed Premiums, Life Insurance in Force	3,297,275,000	3,062,525,000	2,995,079,000
Premiums, Net, Life Insurance in Force	$ 3,093,208,000	$ 2,849,374,000	$ 2,774,377,000
Life Insurance in Force Premiums, Percentage Assumed to Net	106.60%	107.50%	108.00%
Direct Premiums Earned	$ 61,571	$ 57,562	$ 43,106
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	862,903	858,278	843,673
Assumed Premiums Earned	10,642,462	10,049,587	9,371,308
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 9,841,130	$ 9,248,871	$ 8,570,741
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	108.10%	108.70%	109.30%
US Traditional Segment Reporting Information [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Earned	$ 30,500	$ 31,600	$ 29,400
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	610,400	616,000	607,000
Assumed Premiums Earned	5,936,200	5,834,000	5,384,300
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 5,356,300	$ 5,249,600	$ 4,806,700
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	110.80%	111.10%	112.00%
US Non-Traditional Segment Reporting Information [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Earned	$ 4,300	$ 1,600	$ 2,900
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	0	40,200	38,800
Assumed Premiums Earned	19,400	63,000	58,100
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 23,700	$ 24,400	$ 22,200
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	81.90%	258.20%	261.70%
Canada Traditional Segment Reporting Information [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Earned	$ 0	$ 0	$ 0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	38,100	36,500	42,300
Assumed Premiums Earned	940,100	965,100	881,200
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 902,000	$ 928,600	$ 838,900
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	104.20%	103.90%	105.00%
Canada Non-Traditional Segment Reporting Information [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Earned	$ 0	$ 0	$ 0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	0	0	0
Assumed Premiums Earned	38,200	38,700	38,000
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 38,200	$ 38,700	$ 38,000
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	100.00%	100.00%	100.00%
EMEA Traditional Segment Reporting Information [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Earned	$ 26,600	$ 24,100	$ 10,700
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	34,900	30,900	25,500
Assumed Premiums Earned	1,310,000	1,146,900	1,136,300
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 1,301,700	$ 1,140,100	$ 1,121,500
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	100.60%	100.60%	101.30%
EMEA Non-Traditional Segment Reporting Information [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Earned	$ 200	$ 300	$ 100
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	125,000	84,400	89,100
Assumed Premiums Earned	288,500	264,400	260,800
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 163,700	$ 180,300	$ 171,800
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	176.20%	146.60%	151.80%
Asia Pacific Traditional Segment Reporting Information [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Earned	$ 0	$ 0	$ 0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	54,500	50,300	41,000
Assumed Premiums Earned	2,107,500	1,731,800	1,592,600
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 2,053,000	$ 1,681,500	$ 1,551,600
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	102.70%	103.00%	102.60%
Asia Pacific Non-Traditional Segment Reporting Information [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Earned	$ 0	$ 0	$ 0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	0	0	0
Assumed Premiums Earned	2,400	5,400	19,500
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 2,400	$ 5,400	$ 19,500
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	100.00%	100.00%	100.00%
Corporate And Other Segment Reporting Information [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Earned	$ 0	$ 0	$ 0
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	0	0	0
Assumed Premiums Earned	100	300	500
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 100	$ 300	$ 500
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	100.00%	100.00%	100.00%

Valuation and Qualifying Acc167

Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance of Deferred Tax Assets [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation Allowances and Reserves, Balance, Beginning Balance	$ 133.4	$ 127.1	$ 112
Valuation Allowances and Reserves, Charged to Cost and Expense	88.5	11	23.7
Valuation Allowances and Reserves, Charged to Other Accounts	10.6	(4.7)	(8.6)
Valuation Allowances and Reserves, Deductions	5.6	0	0
Valuation Allowances and Reserves, Balance, Ending Balance	226.9	133.4	127.1
Allowance for Loan and Lease Losses, Real Estate [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation Allowances and Reserves, Balance, Beginning Balance	7.7	6.8	6.5
Valuation Allowances and Reserves, Charged to Cost and Expense	1.7	0.9	0.3
Valuation Allowances and Reserves, Charged to Other Accounts	0	0	0
Valuation Allowances and Reserves, Deductions	0	0	0
Valuation Allowances and Reserves, Balance, Ending Balance	$ 9.4	$ 7.7	$ 6.8