Reinsurance Group of America (RGA) 10-Q 4 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document And Entitiy Information [Abstract]
Document Type	10-Q
Document period end date	Mar. 31, 2018
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		64,523,063
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
Fixed maturity securities available-for-sale, at fair value (amortized cost $35,913,705 and $35,281,412)	$ 37,945,260	$ 38,150,820
Available-for-sale Securities, Equity Securities	103,983	100,152
Mortgage loans on real estate (net of allowances of $8,864 and $9,384)	4,437,994	4,400,533
Policy loans	1,346,930	1,357,624
Funds withheld at interest	6,005,892	6,083,388
Short-term investments	130,430	93,304
Other invested assets	1,512,147	1,505,332
Total investments	51,482,636	51,691,153
Cash and cash equivalents	1,510,407	1,303,524
Accrued investment income	408,338	392,721
Premiums receivable and other reinsurance balances	2,620,515	2,338,481
Reinsurance ceded receivables	810,554	782,027
Deferred policy acquisition costs	3,245,851	3,239,824
Other assets	876,522	767,088
Total assets	60,954,823	60,514,818
Liabilities and Stockholders’ Equity
Future policy benefits	22,645,243	22,363,241
Interest-sensitive contract liabilities	16,661,602	16,227,642
Other policy claims and benefits	5,361,149	4,992,074
Other reinsurance balances	483,708	488,739
Deferred income taxes	2,085,631	2,198,309
Other liabilities	1,167,596	1,102,975
Long-term debt	2,788,240	2,788,365
Collateral finance and securitization notes	753,393	783,938
Total liabilities	51,946,562	50,945,283
Commitments and contingent liabilities (See Note 8)
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, 79,137,758 shares issued at March 31, 2018 and December 31, 2017	791	791
Additional paid-in-capital	1,880,352	1,870,906
Retained earnings	6,797,545	6,736,265
Treasury stock, at cost - 14,624,985 and 14,685,663 shares	(1,098,823)	(1,102,058)
Accumulated other comprehensive income	1,428,396	2,063,631
Total stockholders’ equity	9,008,261	9,569,535
Total liabilities and stockholders’ equity	$ 60,954,823	$ 60,514,818

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS PARENTHETICAL - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Available for Sale at Fair value - Amortized cost	$ 35,913,705	$ 35,281,412
Preferred stock par value (per share)	$ 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 (per share)	$ 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	64,512,773	64,452,095
Treasury stock, shares	14,624,985	14,685,663
Allowance for Loan and Lease Losses, Real Estate	$ 8,864	$ 9,384
Available-for-sale Equity Securities, Amortized Cost Basis	$ 110,747	$ 102,841

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Net premiums	$ 2,582,551	$ 2,365,696
Investment income, net of related expenses	516,329	514,364
Investment related gains (losses), net:
Other-than-temporary impairments on fixed maturity securities	0	(17,189)
Other investment related gains (losses), net	(470)	77,712
Total investment related gains (losses), net	(470)	60,523
Other revenues	75,297	68,157
Total revenues	3,173,707	3,008,740
Benefits and Expenses:
Claims and other policy benefits	2,362,101	2,106,145
Interest credited	80,449	107,684
Policy acquisition costs and other insurance expenses	356,902	379,389
Other operating expenses	191,274	158,506
Interest expense	37,454	42,402
Collateral finance and securitization expense	7,602	6,770
Total benefits and expenses	3,035,782	2,800,896
Income before income taxes	137,925	207,844
Provision for income taxes	37,695	62,332
Net income	$ 100,230	$ 145,512
Earnings per share:
Basic earnings per share	$ 1.55	$ 2.26
Diluted earnings per share	1.52	2.22
Dividends declared per share	$ 0.50	$ 0.41

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Comprehensive income (loss)
Net income	$ 100,230	$ 145,512
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(1,160)	(22,213)
Net unrealized investment gains (losses)	(633,604)	203,115
Defined benefit pension and postretirement plan adjustments	(471)	924
Total other comprehensive income (loss), net of tax	(635,235)	181,826
Total comprehensive income (loss)	$ (535,005)	$ 327,338

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows from Operating Activities:
Net income	$ 100,230	$ 145,512
Change in operating assets and liabilities:
Accrued investment income	(10,484)	(10,501)
Premiums receivable and other reinsurance balances	(275,354)	(54,845)
Deferred policy acquisition costs	13,007	58,962
Reinsurance ceded receivable balances	(21,872)	(81,046)
Future policy benefits, other policy claims and benefits, and other reinsurance balances	466,983	396,459
Deferred income taxes	33,715	50,110
Other assets and other liabilities, net	(41,385)	(11,101)
Amortization of net investment premiums, discounts and other	(31,032)	(23,471)
Depreciation, Depletion and Amortization	10,294	6,845
Investment related (gains) losses, net	470	(60,523)
Other, net	(20,823)	964
Net cash provided by operating activities	223,749	417,365
Cash Flows from Investing Activities:
Sales of fixed maturity securities available-for-sale	1,898,722	1,563,956
Maturities of fixed maturity securities available-for-sale	195,549	201,515
Proceeds from Sale of Available-for-sale Securities, Equity	29,683	152,509
Payments to Acquire Mortgage Notes Receivable	(102,002)	(88,835)
Payments to Fund Policy Loans	(10,694)	(24,663)
Payments to Acquire Available-for-sale Securities	1,969,899	1,933,120
Payments to Acquire Available-for-sale Securities, Equity	(2,173)	(14,646)
Proceeds from Sale and Collection of Mortgage Notes Receivable	(141,131)	(184,575)
Increase (Decrease) in Funds Held under Reinsurance Agreements	(19,638)	2,753
Payments to Acquire Businesses, Net of Cash Acquired	24,864	0
Payments to Acquire Property, Plant, and Equipment	(5,292)	(16,893)
Change in short-term investments	(13,026)	23,668
Change in other invested assets	(23,353)	(14,126)
Net cash provided by (used in) investing activities	76,550	(110,967)
Cash Flows from Financing Activities:
Dividends to stockholders	(32,241)	(26,381)
Proceeds from (Repayments of) Secured Debt	(27,104)	(16,908)
Repayments of Long-term Debt	(662)	(300,636)
Purchases of treasury stock	(2,616)	(3,067)
Exercise of stock options, net	1,163	1,719
Change in cash collateral for derivative positions and other arrangements	19,537	(3,628)
Deposits on universal life and other investment type policies and contracts	83,004	202,850
Withdrawals on universal life and other investment type policies and contracts	(156,486)	(201,784)
Net cash used in financing activities	(115,405)	(347,835)
Effect of exchange rate changes on cash	21,989	18,833
Change in cash and cash equivalents	206,883	(22,604)
Cash and cash equivalents, beginning of period	1,303,524	1,200,718
Cash and cash equivalents, end of period	1,510,407	1,178,114
Supplemental disclosures of cash flow information:
Noncash or Part Noncash Acquisition, Value of Assets Acquired	59,184	0
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed	34,320	0
Interest Paid, Net	39,284	46,401
Income Taxes Paid, Net	6,356	12,132
Payments to Acquire Businesses, Gross	(24,864)
Transfer to Investments	$ 605,085	$ 1,653

CONDENSED CONSOLIDATED STATEME7

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS PARENTHETICAL $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Statement of Cash Flows [Abstract]
Cash Acquired from Acquisition	$ 1,733

Business and Basis of Presentat

Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Business and Basis of Presentation Reinsurance Group of America, Incorporated (“RGA”) is an insurance holding company that was formed on December 31, 1992. The accompanying unaudited condensed consolidated financial statements of RGA and its subsidiaries (collectively, the “Company”) have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, these condensed consolidated financial statements do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments, including normal recurring adjustments necessary for a fair presentation have been included. Results for the three months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 . These unaudited condensed consolidated financial statements include the accounts of RGA and its subsidiaries, and all intercompany accounts and transactions have been eliminated. These condensed consolidated statements should be read in conjunction with the Company’s 2017 Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on February 27, 2018 (the “2017 Annual Report”).

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2018
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): Three months ended March 31, 2018 2017 Earnings: Net income (numerator for basic and diluted calculations) $ 100,230 $ 145,512 Shares: Weighted average outstanding shares (denominator for basic calculation) 64,490 64,353 Equivalent shares from outstanding stock options 1,382 1,318 Denominator for diluted calculation 65,872 65,671 Earnings per share: Basic $ 1.55 $ 2.26 Diluted $ 1.52 $ 2.22 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. For the three months ended March 31, 2018 , approximately 0.2 million stock options and approximately 0.2 million performance contingent shares were excluded from the calculation. For the three months ended March 31, 2017 , approximately 0.2 million stock options and approximately 0.5 million performance contingent shares were excluded from the calculation.

Equity

Equity	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Stockholders' Equity Note Disclosure [Text Block]	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, 2017 79,137,758 14,685,663 64,452,095 Stock-based compensation (1) — (60,678 ) 60,678 Balance, March 31, 2018 79,137,758 14,624,985 64,512,773 Issued Held In Treasury Outstanding Balance, December 31, 2016 79,137,758 14,835,256 64,302,502 Stock-based compensation (1) — (86,049 ) 86,049 Balance, March 31, 2017 79,137,758 14,749,207 64,388,551 (1) Represents net shares issued from treasury pursuant to the Company’s equity-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. On January 26, 2017, RGA’s board of directors authorized a share repurchase program for up to $400.0 million of RGA’s outstanding common stock. The authorization was effective immediately and does not have an expiration date. During the three months ended March 31, 2018 and 2017 , no common stock was repurchased by RGA under this program. Accumulated Other Comprehensive Income (Loss) The balance of and changes in each component of accumulated other comprehensive income (loss) (“AOCI”) for the three months ended March 31, 2018 and 2017 are as follows (dollars in thousands): Accumulated Other Comprehensive Income (Loss), Net of Income Tax Accumulated Currency Translation Adjustments Unrealized Appreciation (Depreciation) of Investments (1) Pension and Postretirement Benefits Total Balance, December 31, 2017 $ (86,350 ) $ 2,200,661 $ (50,680 ) $ 2,063,631 Other comprehensive income (loss) before reclassifications 5,696 (827,701 ) (1,910 ) (823,915 ) Amounts reclassified to AOCI — 21,274 1,346 22,620 Deferred income tax benefit (expense) (6,856 ) 172,823 93 166,060 Balance, March 31, 2018 $ (87,510 ) $ 1,567,057 $ (51,151 ) $ 1,428,396 Accumulated Other Comprehensive Income (Loss), Net of Income Tax Accumulated Currency Translation Adjustments Unrealized Appreciation (Depreciation) of Investments (1) Pension and Postretirement Benefits Total Balance, December 31, 2016 $ (172,541 ) $ 1,355,033 $ (43,163 ) $ 1,139,329 Other comprehensive income (loss) before reclassifications (50,735 ) 283,443 (27 ) 232,681 Amounts reclassified to AOCI — 5,762 1,456 7,218 Deferred income tax benefit (expense) 28,522 (86,090 ) (505 ) (58,073 ) Balance, March 31, 2017 $ (194,754 ) $ 1,558,148 $ (42,239 ) $ 1,321,155 (1) Includes cash flow hedges of $20,662 and $2,619 as of March 31, 2018 and December 31, 2017 , respectively, and $7,690 and $(2,496) as of March 31, 2017 and December 31, 2016 , respectively. See Note 5 - “Derivative Instruments” for additional information on cash flow hedges. The following table presents the amounts of AOCI reclassifications for the three months ended March 31, 2018 and 2017 (dollars in thousands): Amount Reclassified from AOCI Three months ended March 31, Details about AOCI Components 2018 2017 Affected Line Item in Statement of Income Net unrealized investment gains (losses): Net unrealized gains (losses) on available-for-sale securities $ (14,456 ) $ (11,857 ) Investment related gains (losses), net Cash flow hedges - Interest rate (370 ) — (1) Cash flow hedges - Currency/Interest rate 144 197 (1) Cash flow hedges - Forward bond purchase commitments — 50 (1) Deferred policy acquisition costs attributed to unrealized gains and losses (6,592 ) 5,848 (2) Total (21,274 ) (5,762 ) Provision for income taxes 4,678 3,194 Net unrealized gains (losses), net of tax $ (16,596 ) $ (2,568 ) Amortization of defined benefit plan items: Prior service cost (credit) $ 246 $ 82 (3) Actuarial gains/(losses) (1,592 ) (1,538 ) (3) Total (1,346 ) (1,456 ) Provision for income taxes 283 510 Amortization of defined benefit plans, net of tax $ (1,063 ) $ (946 ) Total reclassifications for the period $ (17,659 ) $ (3,514 ) (1) See Note 5 - “Derivative Instruments” for additional information on cash flow hedges. (2) This AOCI component is included in the computation of the deferred policy acquisition cost. See Note 8 – “Deferred Policy Acquisition Costs” of the 2017 Annual Report for additional details. (3) This AOCI component is included in the computation of the net periodic pension cost. See Note 10 – “Employee Benefit Plans” for additional deta

Equity Based Compensation

Equity Based Compensation	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity Based Compensation	ity compensation expense was $9.7 million and $9.6 million for the three months ended March 31, 2018 and 2017 , respectively. In the first quarter of 2018, the Company granted 0.2 million stock appreciation rights at $150.87 weighted average exercise price per share and 0.1 million performance contingent units to employees. Additionally, non-employee directors were granted a total of 7,263 shares of common stock. As of March 31, 2018 , 1.7 million share options at a weighted average strike price per share of $68.51 were vested and exercisable, with a remaining weighted average exercise period of 4.9 years.

Investments

Investments	3 Months Ended
	Mar. 31, 2018
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 table provides information relating to investments in fixed maturity securities by sector as of March 31, 2018 (dollars in thousands): March 31, 2018: Amortized Unrealized Unrealized Estimated Fair % of Other-than- Cost Gains Losses Value Total in AOCI Available-for-sale: Corporate $ 22,890,985 $ 869,867 $ 240,383 $ 23,520,469 61.9 % $ — Canadian government 2,803,077 1,297,817 3,040 4,097,854 10.8 — RMBS 1,791,007 23,640 27,499 1,787,148 4.7 — ABS 1,727,810 16,383 9,471 1,734,722 4.6 275 CMBS 1,281,452 12,717 12,236 1,281,933 3.4 — U.S. government 1,486,262 9,266 59,414 1,436,114 3.8 — State and political subdivisions 672,064 49,465 8,016 713,513 1.9 — Other foreign government 3,261,048 133,865 21,406 3,373,507 8.9 — Total fixed maturity securities $ 35,913,705 $ 2,413,020 $ 381,465 $ 37,945,260 100.0 % $ 275 The following table provides information relating to investments in fixed maturity and equity securities by sector as of December 31, 2017 (dollars in thousands): December 31, 2017: Amortized Unrealized Unrealized Estimated Fair % of Other-than- Cost Gains Losses Value Total 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 % 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 condensed consolidated balance sheets. Fixed maturity securities received as collateral are held in separate custodial accounts and are not recorded on the Company’s condensed consolidated balance sheets. Subject to certain constraints, the Company is permitted by contract to sell or repledge collateral it receives; however, as of March 31, 2018 and December 31, 2017 , 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 March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Fixed maturity securities pledged as collateral $ 72,850 $ 75,384 $ 72,542 $ 75,622 Fixed maturity securities received as collateral n/a 614,423 n/a 590,417 Assets in trust held to satisfy collateral requirements 16,316,662 17,076,547 15,584,296 16,715,281 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 March 31, 2018 and December 31, 2017 (dollars in thousands). March 31, 2018 December 31, 2017 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Fixed maturity securities guaranteed or issued by: Canadian province of Quebec $ 1,106,753 $ 1,863,568 $ 1,119,337 $ 1,917,996 Canadian province of Ontario 928,384 1,247,158 939,837 1,282,944 The amortized cost and estimated fair value of fixed maturity securities classified as available-for-sale at March 31, 2018 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 $ 900,166 $ 905,385 Due after one year through five years 7,939,821 8,084,053 Due after five years through ten years 9,533,025 9,779,934 Due after ten years 12,740,424 14,372,085 Asset and mortgage-backed securities 4,800,269 4,803,803 Total $ 35,913,705 $ 37,945,260 Corporate Fixed Maturity Securities The tables below show the major industry types of the Company’s corporate fixed maturity holdings as of March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018: Estimated Amortized Cost Fair Value % of Total Finance $ 8,250,681 $ 8,407,037 35.8 % Industrial 12,093,034 12,437,180 52.8 Utility 2,547,270 2,676,252 11.4 Total $ 22,890,985 $ 23,520,469 100.0 % December 31, 2017: Estimated Amortized Cost 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 % Other-Than-Temporary Impairments - Fixed Maturity Securities As discussed in Note 2 – “Summary of Significant Accounting Policies” of the 2017 Annual Report, 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 condensed 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): Three months ended March 31, 2018 2017 Balance, beginning of period $ 3,677 $ 6,013 Credit loss OTTI previously recognized on securities impaired to fair value during the period — (2,336 ) Balance, end of period $ 3,677 $ 3,677 Unrealized Losses for Fixed Maturity and Equity Securities Available-for-Sale The following table presents the total gross unrealized losses for the 2,114 fixed maturity securities as of March 31, 2018 , where the estimated fair value had declined and remained below amortized cost by the indicated amount (dollars in thousands): March 31, 2018 Gross Unrealized Losses % of Total Less than 20% $ 358,873 94.1 % 20% or more for less than six months 20,232 5.3 20% or more for six months or greater 2,360 0.6 Total $ 381,465 100.0 % The following table presents the total gross unrealized losses for the 1,116 fixed maturity and equity securities at December 31, 2017 where the estimated fair value had declined and remained below amortized cost by the indicated amount (dollars in thousands): December 31, 2017 Gross % of Total Less than 20% $ 113,466 97.0 % 20% or more for less than six months 689 0.6 20% or more for six months or greater 2,838 2.4 Total $ 116,993 100.0 % 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. The following table presents the estimated fair values and gross unrealized losses, including other-than-temporary impairment losses reported in AOCI, for 2,114 fixed maturity securities that have estimated fair values below amortized cost as of March 31, 2018 (dollars in thousands). 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. Less than 12 months 12 months or greater Total Gross Gross Gross March 31, 2018: Estimated Unrealized Estimated Unrealized Estimated Unrealized Fair Value Losses Fair Value Losses Fair Value Losses Investment grade securities: Corporate $ 7,282,079 $ 155,541 $ 883,699 $ 46,908 $ 8,165,778 $ 202,449 Canadian government 39,192 390 109,552 2,536 148,744 2,926 RMBS 897,255 19,899 225,288 7,575 1,122,543 27,474 ABS 612,053 7,001 114,605 2,423 726,658 9,424 CMBS 538,464 8,026 103,447 4,210 641,911 12,236 U.S. government 488,095 16,856 744,844 42,558 1,232,939 59,414 State and political subdivisions 135,158 3,331 67,949 4,685 203,107 8,016 Other foreign government 746,485 15,575 191,446 5,000 937,931 20,575 Total investment grade securities 10,738,781 226,619 2,440,830 115,895 13,179,611 342,514 Below investment grade securities: Corporate 452,086 29,597 46,976 8,337 499,062 37,934 Canadian government 1,900 114 — — 1,900 114 RMBS — — 1,272 25 1,272 25 ABS — — 1,173 47 1,173 47 Other foreign government 57,385 662 12,045 169 69,430 831 Total below investment grade securities 511,371 30,373 61,466 8,578 572,837 38,951 Total fixed maturity securities $ 11,250,152 $ 256,992 $ 2,502,296 $ 124,473 $ 13,752,448 $ 381,465 The following table presents the estimated fair values and gross unrealized losses, including other-than-temporary impairment losses reported in AOCI, for 1,116 fixed maturity and equity securities that have estimated fair values below amortized cost as of December 31, 2017 (dollars in thousands): Less than 12 months 12 months or greater Total Gross Gross Gross December 31, 2017: Estimated Unrealized Estimated Unrealized Estimated Unrealized Fair Value Losses Fair Value Losses Fair Value Losses 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 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 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 March 31, 2018 are primarily related to high-yield corporate securities. Changes in unrealized losses are primarily being driven by changes in interest rates. Investment Income, Net of Related Expenses Major categories of investment income, net of related expenses, consist of the following (dollars in thousands): Three months ended March 31, 2018 2017 Fixed maturity securities available-for-sale $ 369,203 $ 324,500 Equity securities 1,682 1,359 Mortgage loans on real estate 50,199 44,347 Policy loans 14,780 15,272 Funds withheld at interest 75,445 127,578 Short-term investments and cash and cash equivalents 3,245 1,510 Other 23,828 18,468 Investment income 538,382 533,034 Investment expense (22,053 ) (18,670 ) Investment income, net of related expenses $ 516,329 $ 514,364 Investment Related Gains (Losses), Net Investment related gains (losses), net consist of the following (dollars in thousands): Three months ended March 31, 2018 2017 Fixed maturity securities available for sale: Other-than-temporary impairment losses on fixed maturity securities recognized in earnings $ — $ (17,189 ) Gain on investment activity 10,966 17,893 Loss on investment activity (20,380 ) (8,687 ) Equity securities: Gain on investment activity 28 — Loss on investment activity (950 ) (3,876 ) Change in unrealized gains (losses) recognized in earnings (4,137 ) — Other impairment losses and change in mortgage loan provision (312 ) (99 ) Derivatives and other, net 14,315 72,481 Total investment related gains (losses), net $ (470 ) $ 60,523 There were no fixed maturity impairments for the three months ended March 31, 2018 . The fixed maturity impairments for the three months ended March 31, 2017 were largely related to high-yield corporate securities. The other impairment losses and change in mortgage loan provision for the three months ended March 31, 2018 were primarily due to impairments on real estate joint ventures offset by a release of the mortgage loan valuation allowance. The other impairment losses and change in mortgage loan provision for the three months ended March 31, 2017 were primarily due to an increase in the mortgage loan valuation allowance. The fluctuations in investment related gains (losses) for derivatives and other for the three months ended March 31, 2018 , compared to the same period in 2017 , are primarily due to changes in the fair value of embedded derivatives and interest rate swaps. During the three months ended March 31, 2018 and 2017 , the Company sold fixed maturity securities with fair values of $1,263.6 million and $428.6 million at losses of $20.4 million and $8.7 million , respectively. During the three months ended March 31, 2018 and 2017 , the Company sold equity securities with fair values of $28.4 million and $147.6 million at losses of $1.0 million and $3.9 million , respectively. The Company generally does not buy and sell securities on a short-term basis. Securities Borrowing, Lending and Other The following table includes the amount of borrowed securities, securities lent and securities collateral received as part of the securities lending program and repurchased/reverse repurchased securities pledged and received as of March 31, 2018 and December 31, 2017 (dollars in thousands). March 31, 2018 December 31, 2017 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Borrowed securities $ 353,875 $ 370,760 $ 358,875 $ 377,820 Securities lending: Securities loaned 117,449 118,617 117,246 121,551 Securities received n/a 128,000 n/a 128,000 Repurchase program/reverse repurchase program: Securities pledged 403,135 411,988 413,819 428,344 Securities received n/a 404,871 n/a 417,550 The Company also held cash collateral for repurchase program/reverse repurchase programs of $30.7 million and $31.2 million at March 31, 2018 and December 31, 2017 , respectively. No cash or securities have been pledged by the Company for its securities borrowing program as of March 31, 2018 and December 31, 2017 . The following table presents information on the Company’s securities lending and repurchase transactions as of March 31, 2018 and December 31, 2017 (dollars in thousands). Collateral associated with certain borrowed securities is not included within the table, as the collateral pledged to each counterparty is the right to reinsurance treaty cash flows. March 31, 2018 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total Securities lending transactions: Corporate $ — $ — $ — $ 118,617 $ 118,617 Total $ — $ — $ — $ 118,617 $ 118,617 Repurchase transactions: Corporate $ — $ — $ — $ 171,678 $ 171,678 RMBS — — — — — U.S. government — — — 219,509 219,509 Foreign government — — — 19,670 19,670 Other 1,131 — — — 1,131 Total 1,131 — — 410,857 411,988 Total borrowings $ 1,131 $ — $ — $ 529,474 $ 530,605 Gross amount of recognized liabilities for securities lending and repurchase transactions in preceding table $ 563,587 Amounts related to agreements not included in offsetting disclosure $ 32,982 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 transactions: 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 borrowings $ 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 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 condensed consolidated balance sheets was a liability of $0.4 million and $1.1 million as of March 31, 2018 and December 31, 2017 , respectively. As of March 31, 2018 and December 31, 2017 , 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 8.6% and 8.5% of the Company’s total investments as of March 31, 2018 and December 31, 2017 . As of March 31, 2018 , mortgage loans were geographically dispersed throughout the U.S. with the largest concentrations in California ( 19.6% ), Texas ( 8.6% ) and Georgia ( 7.5% ) and include loans secured by properties in Canada ( 2.4% ). 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 March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 Property type: Carrying Value % of Total Carrying Value % of Total Office building $ 1,518,170 34.1 % $ 1,487,392 33.6 % Retail 1,236,933 27.8 1,270,676 28.8 Industrial 964,685 21.7 938,612 21.3 Apartment 497,699 11.2 510,052 11.6 Other commercial 232,804 5.2 206,439 4.7 Recorded investment 4,450,291 100.0 % $ 4,413,171 100.0 % Unamortized balance of loan origination fees and expenses (3,433 ) (3,254 ) Valuation allowances (8,864 ) (9,384 ) Total mortgage loans on real estate $ 4,437,994 $ 4,400,533 The maturities of the mortgage loans as of March 31, 2018 and December 31, 2017 are as follows (dollars in thousands): March 31, 2018 December 31, 2017 Recorded Investment % of Total Recorded Investment % of Total Due within five years $ 1,130,108 25.4 % $ 1,091,066 24.8 % Due after five years through ten years 2,492,588 56.0 2,516,872 57.0 Due after ten years 827,595 18.6 805,233 18.2 Total $ 4,450,291 100.0 % $ 4,413,171 100.0 % The following tables set forth certain key credit quality indicators of the Company’s recorded investment in mortgage loans as of March 31, 2018 and December 31, 2017 (dollars in thousands): Recorded Investment Debt Service Ratios Construction loans >1.20x 1.00x - 1.20x <1.00x Total % of Total March 31, 2018: Loan-to-Value Ratio 0% - 59.99% $ 2,154,344 $ 79,738 $ 6,855 $ 12,279 $ 2,253,216 50.6 % 60% - 69.99% 1,520,008 29,795 68,070 — 1,617,873 36.4 70% - 79.99% 360,183 27,682 30,904 — 418,769 9.4 Greater than 80% 125,660 30,497 4,276 — 160,433 3.6 Total $ 4,160,195 $ 167,712 $ 110,105 $ 12,279 $ 4,450,291 100.0 % 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 % The age analysis of the Company’s past due recorded investments in mortgage loans as of March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 31-60 days past due $ 17,102 $ 17,100 61-90 days past due — 2,056 Greater than 90 days 2,056 — Total past due 19,158 19,156 Current 4,431,133 4,394,015 Total $ 4,450,291 $ 4,413,171 The following table presents the recorded investment in mortgage loans, by method of measuring impairment, and the related valuation allowances as of March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 Mortgage loans: Individually measured for impairment $ 23,423 $ 5,858 Collectively measured for impairment 4,426,868 4,407,313 Recorded investment $ 4,450,291 $ 4,413,171 Valuation allowances: Individually measured for impairment $ — $ — Collectively measured for impairment 8,864 9,384 Total valuation allowances $ 8,864 $ 9,384 Information regarding the Company’s loan valuation allowances for mortgage loans for the three months ended March 31, 2018 and 2017 is as follows (dollars in thousands): Three months ended March 31, 2018 2017 Balance, beginning of period $ 9,384 $ 7,685 Provision (release) (516 ) 101 Translation adjustment (4 ) — Balance, end of period $ 8,864 $ 7,786 Information regarding the portion of the Company’s mortgage loans that were impaired as of March 31, 2018 and December 31, 2017 is as follows (dollars in thousands): Unpaid Principal Balance Recorded Investment Related Allowance Carrying Value March 31, 2018: Impaired mortgage loans with no valuation allowance recorded $ — $ 23,423 $ — $ 23,423 Impaired mortgage loans with valuation allowance recorded — — — — Total impaired mortgage loans $ — $ 23,423 $ — $ 23,423 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 The Company’s average investment balance of impaired mortgage loans and the related interest income are reflected in the table below for the periods indicated (dollars in thousands): Three months ended March 31, 2018 2017 Average (1) Interest Income Average (1) Interest Income Impaired mortgage loans with no valuation allowance recorded $ 14,640 $ 56 $ 2,157 $ 33 Impaired mortgage loans with valuation allowance recorded — — — — Total impaired mortgage loans $ 14,640 $ 56 $ 2,157 $ 33 (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 three months ended March 31, 2018 and 2017 . The Company had no mortgage loans that were on a nonaccrual status as of March 31, 2018 and December 31, 2017 . Policy Loans Policy loans comprised approximately 2.6% of the Company’s total investments as of March 31, 2018 and December 31, 2017 , 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 11.7% and 11.8% of the Company’s total investments as of March 31, 2018 and December 31, 2017 , respectively. Of the $6.0 billion funds withheld at interest balance, net of embedded derivatives, as of March 31, 2018 , $4.0 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 condensed 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 limited partnership interests, joint ventures (other than operating joint ventures), equity release mortgages, derivative contracts and fair value option (“FVO”) contractholder-directed unit-linked investments. Other invested assets also include FHLB common stock, which is included in other in the table below. Other invested assets represented approximately 2.9% of the Company’s total investments as of March 31, 2018 and December 31, 2017 . Carrying values of these assets as of March 31, 2018 and December 31, 2017 are as follows (dollars in thousands): March 31, 2018 December 31, 2017 Limited partnership interests and real estate joint ventures 805,613 781,124 Equity release mortgages 261,837 219,940 Derivatives 132,195 137,613 FVO contractholder-directed unit-linked investments 221,512 218,541 Other 90,990 148,114 Total other invested assets $ 1,512,147 $ 1,505,332

Derivative Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2018
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 condensed consolidated balance sheets in other invested assets or other liabilities, at fair value. Longevity and mortality swaps are included on the condensed 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 condensed 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 condensed 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 March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 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 $ 1,021,739 $ 47,303 $ 152 $ 996,204 $ 59,809 $ 2,372 Financial futures 388,874 — — 412,438 — — Foreign currency forwards 6,012 48 4 6,030 — 28 Consumer price index swaps 218,237 127 427 221,932 — 2,160 Credit default swaps 933,200 7,279 1,058 961,200 8,319 1,651 Equity options 639,801 33,958 — 632,251 23,271 — Longevity swaps 985,920 44,011 — 960,400 40,659 — Mortality swaps — — 1,683 — — 1,683 Synthetic guaranteed investment contracts 10,866,171 — — 10,052,576 — — Embedded derivatives in: Modified coinsurance or funds withheld arrangements — 135,805 — — 122,194 — Indexed annuity products — — 827,109 — — 861,758 Variable annuity products — — 137,686 — — 152,470 Total non-hedging derivatives 15,059,954 268,531 968,119 14,243,031 254,252 1,022,122 Derivatives designated as hedging instruments: Interest rate swaps 435,000 (1,119 ) 16,972 435,000 — 20,389 Foreign currency swaps 598,575 56,403 5,461 672,921 65,207 8,496 Foreign currency forwards 698,241 7,458 225 553,175 1,265 7,720 Total hedging derivatives 1,731,816 62,742 22,658 1,661,096 66,472 36,605 Total derivatives $ 16,791,770 $ 331,273 $ 990,777 $ 15,904,127 $ 320,724 $ 1,058,727 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 condensed 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 March 31, 2018 and December 31, 2017 (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 March 31, 2018: Derivative assets $ 195,468 $ (19,262 ) $ 176,206 $ — $ (188,407 ) $ (12,201 ) Derivative liabilities 25,982 (19,262 ) 6,720 (57,456 ) (3,470 ) (54,206 ) 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 ) (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 March 31, 2018 and December 31, 2017 , 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” of the Company’s 2017 Annual Report 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 March 31, 2018 and 2017, 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 three months ended March 31, 2018: Foreign currency swaps Foreign-denominated fixed maturity securities $ (1,891 ) $ 1,891 $ — For the three months ended March 31, 2017: Foreign currency swaps Foreign-denominated fixed maturity securities $ 6,536 $ (6,536 ) $ — 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 three months ended March 31, 2018 and 2017 , $2.4 million and $1.0 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 condensed consolidated income statement classification where the gain or loss is recognized related to cash flow hedges for the three months ended March 31, 2018 and 2017 (dollars in thousands): Three months ended March 31, 2018 2017 Balance beginning of period $ 2,619 $ (2,496 ) Gains (losses) deferred in other comprehensive income (loss) on the effective portion of cash flow hedges 17,817 10,433 Amounts reclassified to investment income (144 ) (247 ) Amounts reclassified to interest expense 370 — Balance end of period $ 20,662 $ 7,690 As of March 31, 2018 , 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 $0.6 million and $0.7 million in investment income and interest expense, respectively. The following table presents the effective portion of derivatives in cash flow hedging relationships on the condensed consolidated statements of income and the condensed consolidated statements of comprehensive income for the three months ended March 31, 2018 and 2017 (dollars in thousands): Effective Portion Derivative Type Gain (Loss) Deferred in OCI Gain (Loss) Reclassified into Income from OCI Investment Income Interest Expense For the three months ended March 31, 2018: Interest rate $ 14,986 $ — $ (370 ) Currency/Interest rate 2,831 144 — Forward bond purchase commitments — — — Total $ 17,817 $ 144 $ (370 ) For the three months ended March 31, 2017: Interest rate $ 2,216 $ — $ — Currency/Interest rate 8,217 197 — Forward bond purchase commitments — 50 — Total $ 10,433 $ 247 $ — All components of each derivative’s gain or loss were included in the assessment of hedge effectiveness. For the three months ended March 31, 2018 and 2017 , 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 three months ended March 31, 2018 and 2017 (dollars in thousands): Derivative Gains (Losses) Deferred in AOCI For the three months ended March 31, Type of NIFO Hedge (1) (2) 2018 2017 Foreign currency swaps $ 8,805 $ (7,606 ) Foreign currency forwards 12,236 — (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 $134.7 million and $113.7 million at March 31, 2018 and December 31, 2017 , respectively. If a hedged foreign operation was sold or substantially liquidated, the amounts in AOCI would be reclassified to the condensed 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 condensed consolidated statements of income, except where otherwise noted. A summary of the effect of non-hedging derivatives, including embedded derivatives, on the Company’s condensed consolidated statements of income for the three months ended March 31, 2018 and 2017 is as follows (dollars in thousands): Gain (Loss) for the three months ended March 31, Type of Non-hedging Derivative Income Statement Location of Gain (Loss) 2018 2017 Interest rate swaps Investment related gains (losses), net $ (26,571 ) $ (2,612 ) Financial futures Investment related gains (losses), net 129 (12,775 ) Foreign currency forwards Investment related gains (losses), net 323 904 CPI swaps Investment related gains (losses), net 2,186 (5 ) Credit default swaps Investment related gains (losses), net (402 ) 7,358 Equity options Investment related gains (losses), net 2,593 (17,189 ) Longevity swaps Other revenues 2,267 1,865 Mortality swaps Other revenues — (395 ) Subtotal (19,475 ) (22,849 ) Embedded derivatives in: Modified coinsurance or funds withheld arrangements Investment related gains (losses), net 13,611 68,702 Indexed annuity products Interest credited 25,351 (16,402 ) Variable annuity products Investment related gains (losses), net 14,785 22,363 Total non-hedging derivatives $ 34,272 $ 51,814 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. Financial Futures Exchange-traded futures are used primarily to economically hedge liabilities embedded in certain variable annuity products. With exchange-traded futures transactions, the Company agrees to purchase or sell a specified number of contracts, the value of which is determined by the relevant 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 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. 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 have been 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 March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 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 Value of Credit Default Swaps Maximum Amount of Future Payments under Credit Default Swaps (2) Weighted Average Years to Maturity (3) AAA/AA+/AA/AA-/A+/A/A- Single name credit default swaps $ 2,761 $ 152,000 3.0 $ 3,128 $ 162,000 2.9 Subtotal 2,761 152,000 3.0 3,128 162,000 2.9 BBB+/BBB/BBB- Single name credit default swaps 4,203 333,700 2.8 4,469 361,700 2.9 Credit default swaps referencing indices 156 422,600 3.7 (55 ) 422,600 4.0 Subtotal 4,359 756,300 3.3 4,414 784,300 3.5 BB+/BB/BB- Single name credit default swaps (25 ) 15,000 1.5 30 5,000 1.5 Subtotal (25 ) 15,000 1.5 30 5,000 1.5 Total $ 7,095 $ 923,300 3.2 $ 7,572 $ 951,300 3.4 (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 March 31, 2018 . 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 (“modco”) 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 (“CVA”) did not have a material effect on the change in fair value of its embedded derivatives for the three months ended March 31, 2018 and 2017 . The related gains (losses) and the effect on net income after amortization of deferred acquisition costs (“DAC”) and income taxes for the three months ended March 31, 2018 and 2017 are reflected in the following table (dollars in thousands): Three months ended March 31, 2018 2017 Embedded derivatives in modco or funds withheld arrangements included in investment related gains $ 13,611 $ 68,702 After the associated amortization of DAC and taxes, the related amounts included in net income 6,850 25,844 Embedded derivatives in variable annuity contracts included in investment related gains 14,785 22,363 After the associated amortization of DAC and taxes, the related amounts included in net income 11,126 28,836 Amounts related to embedded derivatives in equity-indexed annuities included in benefits and expenses 25,351 (16,402 ) After the associated amortization of DAC and taxes, the related amounts included in net income 6,537 (21,396 ) 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 March 31, 2018 and December 31, 2017 are reflected in the following table (dollars in thousands): March 31, 2018 December 31, 2017 Estimated fair value of derivatives in net asset position $ 171,169 $ 155,714 Cash provided as collateral (1) 3,470 22,221 Securities pledged to counterparties as collateral (2) 57,456 58,156 Cash pledged from counterparties as collateral (3) (188,407 ) (185,900 ) Securities pledged from counterparties as collateral (4) — (862 ) Initial margin for cleared derivatives (2) (57,456 ) (58,156 ) Net amount after application of master netting agreements and collateral $ (13,768 ) $ (8,827 ) Margin account related to exchange-traded futures (5) $ 7,382 $ 6,538 (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 securities. (5) Included in other assets.

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Disclosures	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. 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. 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. 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 what other market participants would use when pricing similar assets and 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. For a discussion of the Company’s valuation methodologies for assets and liabilities measured at fair value and the fair value hierarchy, see Note 6 in the Notes to Consolidated Financial Statements included in the Company’s 2017 Annual Report. Assets and Liabilities by Hierarchy Level Assets and liabilities measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017 are summarized below (dollars in thousands): March 31, 2018: Fair Value Measurements Using: Total Level 1 Level 2 Level 3 Assets: Fixed maturity securities – available-for-sale: Corporate $ 23,520,469 $ — $ 22,221,205 $ 1,299,264 Canadian government 4,097,854 — 3,525,107 572,747 RMBS 1,787,148 — 1,666,534 120,614 ABS 1,734,722 — 1,604,016 130,706 CMBS 1,281,933 — 1,280,049 1,884 U.S. government 1,436,114 1,313,806 101,255 21,053 State and political subdivisions 713,513 — 671,637 41,876 Other foreign government 3,373,507 — 3,368,503 5,004 Total fixed maturity securities – available-for-sale 37,945,260 1,313,806 34,438,306 2,193,148 Equity securities 103,983 67,831 — 36,152 Funds withheld at interest – embedded derivatives 135,805 — — 135,805 Cash equivalents 538,761 538,761 — — Short-term investments 58,499 67 55,215 3,217 Other invested assets: Derivatives: Interest rate swaps 40,812 — 40,812 — Foreign currency forwards 6,932 — 6,932 — CPI swaps (99 ) — (99 ) — Credit default swaps 5,465 — 5,465 — Equity options 27,140 — 27,140 — Foreign currency swaps 51,945 — 51,945 — FVO contractholder-directed unit-linked investments 221,512 221,043 469 — Total other invested assets 353,707 221,043 132,664 — Other assets - longevity swaps 44,011 — — 44,011 Total $ 39,180,026 $ 2,141,508 $ 34,626,185 $ 2,412,333 Liabilities: Interest sensitive contract liabilities – embedded derivatives $ 964,795 $ — $ — $ 964,795 Other liabilities: Derivatives: Interest rate swaps 11,752 — 11,752 — Foreign currency forwards (345 ) — (345 ) — CPI swaps 201 — 201 — Credit default swaps (756 ) — (756 ) — Equity options (6,818 ) — (6,818 ) — Foreign currency swaps 1,003 — 1,003 — Mortality swaps 1,683 — — 1,683 Total $ 971,515 $ — $ 5,037 $ 966,478 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 Equity securities: Non-redeemable preferred stock 39,806 39,806 — — Other equity securities 60,346 60,346 — — 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: 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 356,154 217,618 138,536 — 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 Transfers between Levels 1 and 2 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 the quarter ended March 31, 2018. 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. The following tables present the transfers between Level 1 and Level 2 during the three months ended March 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 $ — $ 38,675 Quantitative Information Regarding Internally - Priced Level 3 Assets and Liabilities 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 March 31, 2018 and December 31, 2017 (dollars in thousands): Estimated Fair Value Valuation Technique Unobservable Inputs Range (Weighted Average) March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 Assets: Corporate $183,680 $173,579 Market comparable securities Liquidity premium 0-2% (1%) 0-2% (1%) EBITDA Multiple 5.9X - 7.5X (6.6X) — U.S. government 21,053 22,511 Market comparable securities Liquidity premium 0-1% (1%) 0-1% (1%) State and political subdivisions 4,452 4,616 Market comparable securities Liquidity premium 1 % 1 % Equity securities 25,987 — Market comparable securities Liquidity premium 3% — EBITDA Multiple 6.9X - 13.1X (8.0X) — Funds withheld at interest- embedded derivatives 135,805 122,194 Total return swap Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (9%) Withdrawal 0-5% (3%) 0-5% (3%) CVA 0-5% (1%) 0-5% (1%) Crediting rate 2-4% (2%) 2-4% (2%) Longevity swaps 44,011 40,659 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 827,109 861,758 Discounted cash flow Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (9%) Withdrawal 0-5% (3%) 0-5% (3%) Option budget projection 2-4% (2%) 2-4% (2%) Interest sensitive contract liabilities- embedded derivatives- variable annuities 137,686 152,470 Discounted cash flow Mortality 0-100% (1%) 0-100% (1%) Lapse 0-25% (5%) 0-25% (5%) Withdrawal 0-7% (4%) 0-7% (3%) CVA 0-5% (1%) 0-5% (1%) Long-term volatility 0-27% (13%) 0-27% (8%) Mortality swaps 1,683 1,683 Discounted cash flow Mortality 0-100% (1%) 0-100% (1%) Changes in Level 3 Assets and Liabilities Assets and liabilities transferred into Level 3 are due to a lack of observable market transactions and price information. 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, 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 had previously had below investment-grade ratings. The Company also transferred equity securities with a fair value of approximately $38.9 million into Level 3 as a result of the adoption of the new accounting guidance for the recognition and measurement of equity securities. For further information on the Company’s valuation processes, see Note 6 in the Notes to Consolidated Financial Statements included in the Company’s 2017 Annual Report. The reconciliations for all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) are as follows (dollars in thousands): For the three months ended March 31, 2018: Fixed maturity securities - available-for-sale Corporate Canadian government RMBS ABS Fair value, beginning of period $ 1,337,272 $ 593,942 $ 107,882 $ 123,474 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (361 ) 3,444 (92 ) 106 Investment related gains (losses), net — — — 2 Included in other comprehensive income (32,852 ) (24,639 ) (1,110 ) 853 Purchases (1) 100,170 — 20,916 11,000 Sales (1) (6,180 ) — — — Settlements (1) (75,146 ) — (2,963 ) (2,739 ) Transfers into Level 3 7,166 — — — Transfers out of Level 3 (30,805 ) — (4,019 ) (1,990 ) Fair value, end of period $ 1,299,264 $ 572,747 $ 120,614 $ 130,706 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 $ (361 ) $ 3,444 $ (92 ) $ 106 For the three months ended March 31, 2018 (continued): Fixed maturity securities - available-for-sale CMBS U.S. government State Other foreign government Fair value, beginning of period $ 3,234 $ 22,511 $ 41,203 $ 5,092 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses — (110 ) 8 — Included in other comprehensive income (47 ) (340 ) 700 (88 ) Purchases (1) — 96 — — Settlements (1) (1 ) (1,104 ) (35 ) — Transfers out of Level 3 (1,302 ) — — — Fair value, end of period $ 1,884 $ 21,053 $ 41,876 $ 5,004 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 $ — $ (110 ) $ 8 $ — For the three months ended March 31, 2018 (continued): Equity securities Funds withheld at interest- embedded derivatives Short-term Investments Other assets - longevity swaps Interest sensitive contract liabilities embedded derivatives Other liabilities - mortality swaps Fair value, beginning of period $ — $ 122,194 $ 3,096 $ 40,659 $ (1,014,229 ) $ (1,683 ) Total gains/losses (realized/unrealized) Included in earnings, net: Investment related gains (losses), net (2,677 ) 13,611 — — 14,785 — Interest credited — — — — 25,351 — Included in other comprehensive income — — (25 ) 1,085 — — Other revenues — — — 2,267 — — Purchases (1) — — 146 — (8,508 ) — Sales (1) (28 ) — — — — — Settlements (1) (48 ) — — — 17,807 — Transfers into Level 3 38,905 — — — — — Fair value, end of period $ 36,152 $ 135,805 $ 3,217 $ 44,011 $ (964,794 ) $ (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 income, net of related expenses $ — $ — $ — $ — $ — $ — Investment related gains (losses), net (2,705 ) 13,611 — — 12,901 — Other revenues — — — 2,267 — — Interest credited — — — — 7,544 — For the three months ended March 31, 2017: Fixed maturity securities - available-for-sale Corporate Canadian governments RMBS ABS CMBS U.S. government Fair value, beginning of period $ 1,272,253 $ 475,965 $ 160,291 $ 219,280 $ 21,145 $ 24,488 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (423 ) 3,070 (245 ) 1,018 709 (117 ) Investment related gains (losses), net (1,231 ) — 365 — (595 ) — Included in other comprehensive income 4,948 4,525 650 5,767 (83 ) 52 Purchases (1) 45,914 — 16,499 10,849 — 104 Sales (1) — — (10,604 ) — (3,720 ) — Settlements (1) (71,470 ) — (6,784 ) (18,154 ) (5,401 ) (1,053 ) Transfers into Level 3 13,934 — 77 35,258 — — Transfers out of Level 3 — — (16,819 ) (45,582 ) (10,132 ) — Fair value, end of period $ 1,263,925 $ 483,560 $ 143,430 $ 208,436 $ 1,923 $ 23,474 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 $ (423 ) $ 3,070 $ (91 ) $ 161 $ — $ (117 ) Investment related gains (losses), net (1,293 ) — (346 ) — — — For the three months ended March 31, 2017 (continued): Fixed maturity securities available-for-sale State Other foreign government Funds withheld at interest- embedded derivatives Short-term Investments Other assets - longevity swaps Interest sensitive contract liabilities embedded derivatives Other liabilities - mortality swaps Fair value, beginning of period $ 41,666 $ 12,869 $ (22,529 ) $ 3,346 $ 26,958 $ (990,308 ) $ (2,462 ) Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (88 ) — — — — — — Investment related gains (losses), net — — 68,702 — — 22,362 — Interest credited — — — — — (16,402 ) — Included in other comprehensive income (843 ) (191 ) — 33 347 — — Other revenues — — — — 1,865 — (395 ) Purchases (1) — — — 32 — (6,393 ) — Settlements (1) (33 ) (334 ) — (135 ) — 17,811 — Transfers out of Level 3 (6,844 ) — — — — — — Fair value, end of period $ 33,858 $ 12,344 $ 46,173 $ 3,276 $ 29,170 $ (972,930 ) $ (2,857 ) 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 $ (88 ) $ — $ — $ — $ — $ — $ — Investment related gains (losses), net — — 68,702 — — 20,300 — Other revenues — — — — 1,865 — (395 ) Interest credited — — — — — (34,214 ) — (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. Nonrecurring Fair Value Measurements During the three months ended March 31, 2018 and March 31, 2017, the Company did not have any adjustments to its assets or liabilities measured at fair value on a nonrecurring basis that are still held at the reporting date. Fair Value of Financial Instruments The Company is required by general accounting principles for Fair Value Measurements and Disclosures to disclose the fair value of certain financial instruments including those that are not carried at fair value. 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 March 31, 2018 and December 31, 2017 (dollars in thousands). For additional information regarding the methods and significant assumptions used by the Company to estimate these fair values, see Note 6 in the Notes to Consolidated Financial Statements included in the Company’s 2017 Annual Report. 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. March 31, 2018: Carrying Value (1) Estimated Fair Value Fair Value Measurement Using: Level 1 Level 2 Level 3 NAV Assets: Mortgage loans on real estate $ 4,437,994 $ 4,411,472 $ — $ — $ 4,411,472 $ — Policy loans 1,346,930 1,346,930 — 1,346,930 — — Funds withheld at interest 5,865,791 6,098,479 — — 6,098,479 — Cash and cash equivalents 971,646 971,646 971,646 — — — Short-term investments 71,931 71,931 71,931 — — — Other invested assets 690,200 710,009 10,165 68,903 283,205 347,736 Accrued investment income 408,338 408,338 — 408,338 — — Liabilities: Interest-sensitive contract liabilities $ 13,169,951 $ 13,151,162 $ — $ — $ 13,151,162 $ — Long-term debt 2,788,240 2,916,200 — — 2,916,200 — Collateral finance and securitization notes 753,393 692,696 — — 692,696 — December 31, 2017: 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 651,792 679,377 28,540 67,778 247,934 335,125 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 — (1) Carrying values presented herein may differ from those in the Company’s condensed consolidated balance sheets because certain items within the respective financial statement captions may be measured at fair value on a recurring basis.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment Information	Segment Information The accounting policies of the segments are the same as those described in the Summary of Significant Accounting Policies in Note 2 of the consolidated financial statements accompanying the 2017 Annual Report. 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. The Company has geographic-based and business-based operational segments. Geographic-based operations are further segmented into traditional and financial solutions businesses. Information related to revenues, income (loss) before income taxes and total assets of the Company for each reportable segment are summarized below (dollars in thousands): Three months ended March 31, Revenues: 2018 2017 U.S. and Latin America: Traditional $ 1,489,694 $ 1,488,503 Financial Solutions 213,352 298,846 Total 1,703,046 1,787,349 Canada: Traditional 302,319 264,275 Financial Solutions 12,777 11,807 Total 315,096 276,082 Europe, Middle East and Africa: Traditional 393,782 318,086 Financial Solutions 88,143 79,989 Total 481,925 398,075 Asia Pacific: Traditional 614,539 505,230 Financial Solutions 19,846 20,452 Total 634,385 525,682 Corporate and Other 39,255 21,552 Total $ 3,173,707 $ 3,008,740 Three months ended March 31, Income (loss) before income taxes: 2018 2017 U.S. and Latin America: Traditional $ 2,892 $ 29,960 Financial Solutions 67,421 103,586 Total 70,313 133,546 Canada: Traditional 23,707 19,328 Financial Solutions 3,191 3,592 Total 26,898 22,920 Europe, Middle East and Africa: Traditional 15,421 13,976 Financial Solutions 39,164 31,918 Total 54,585 45,894 Asia Pacific: Traditional 22,887 41,688 Financial Solutions 4,021 5,872 Total 26,908 47,560 Corporate and Other (40,779 ) (42,076 ) Total $ 137,925 $ 207,844 Assets: March 31, 2018 December 31, 2017 U.S. and Latin America: Traditional $ 18,839,888 $ 18,603,423 Financial Solutions 16,349,148 15,959,206 Total 35,189,036 34,562,629 Canada: Traditional 4,234,253 4,161,452 Financial Solutions 126,747 126,372 Total 4,361,000 4,287,824 Europe, Middle East and Africa: Traditional 3,385,127 3,099,495 Financial Solutions 5,279,499 5,274,993 Total 8,664,626 8,374,488 Asia Pacific: Traditional 5,095,054 4,915,442 Financial Solutions 1,175,002 1,198,585 Total 6,270,056 6,114,027 Corporate and Other 6,470,105 7,175,850 Total $ 60,954,823 $ 60,514,818

Commitments, Contingencies and

Commitments, Contingencies and Guarantees	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 and December 31, 2017 are presented in the following table (dollars in thousands): March 31, 2018 December 31, 2017 Limited partnership interests and joint ventures $ 482,149 $ 485,197 Commercial mortgage loans 67,837 40,815 Bank loans and private placements 96,808 60,472 Equity release mortgages 132,523 153,937 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. 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 March 31, 2018 , 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 March 31, 2018 (dollars in millions): Commitment Period Maximum Potential Obligation 2023 $ 500.0 2033 450.0 2034 2,000.0 2035 1,314.2 2036 1,932.0 2037 6,750.0 2038 800.0 Other Guarantees RGA has issued guarantees to third parties on behalf of its subsidiaries for the payment of amounts due under certain 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. Additionally, 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 condensed consolidated balance sheets in future policy benefits. 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 March 31, 2018 and December 31, 2017 are reflected in the following table (dollars in thousands): March 31, 2018 December 31, 2017 Treaty guarantees $ 949,443 $ 1,047,449 Treaty guarantees, net of assets in trust 832,487 926,393 Securities borrowing and repurchase arrangements 291,325 294,325 Financing arrangements 77,858 86,183 Lease obligations 1,465 1,662

Income Tax Income Tax

Income Tax Income Tax	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	Income Tax The Company's effective tax rates differed from the applicable U.S. federal income tax statutory rates of 21% and 35% as a result of the following for the three months ended March 31, 2018 and 2017 , respectively (dollars in thousands): Three months ended March 31, 2018 2017 Tax provision at U.S. statutory rate $ 28,964 $ 72,745 Increase (decrease) in income taxes resulting from: U.S. Tax Reform provisional adjustments 775 — Foreign tax rate differing from U.S. tax rate 1,432 (6,153 ) Differences in tax bases in foreign jurisdictions (5,760 ) (3,383 ) Deferred tax valuation allowance 7,947 1,182 Amounts related to tax audit contingencies 835 611 Corporate rate changes 111 (1,237 ) Subpart F 658 186 Foreign tax credits (572 ) (126 ) Global intangible low-taxed income, net of credit 4,409 — Return to provision adjustments — 229 Equity compensation excess benefit (1,114 ) (1,856 ) Other, net 10 134 Total provision for income taxes $ 37,695 $ 62,332 Effective tax rate 27.3 % 30.0 % On December 22, 2017, the Tax Cuts and Jobs Act of 2017 (“U.S. Tax Reform”) was signed into law. 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% to 21%; (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. Companies subject to GILTI have the option to account for the GILTI tax as a period cost if and when incurred, or to recognize deferred taxes for temporary differences including outside basis differences expected to reverse as GILTI. The Company has not yet made a policy election to account for GILTI, but included an estimate of the current GILTI impact in the tax provision. As of March 31, 2018, the Company has not yet completed its accounting for the tax effects of the enactment of the U.S. Tax Reform. The Company continues to gather additional information to account for the effects of U.S. Tax Reform such as information to more precisely compute the pretax deferred tax items upon which the change in rate was applied and refine the necessary valuation allowance related to the foreign tax credits. Also, the Company also continues to monitor new regulatory and accounting guidance which could impact the provisional balances recorded as of December 31, 2017. The effective tax rate for the three months ended March 31, 2018 was higher than the U.S. Statutory rate of 21.0% primarily as a result of income in non-U.S. jurisdictions with higher tax rates than the U.S., the inclusion of U.S. tax related to GILTI and losses in foreign jurisdictions for which the company established a valuation allowance. The higher rate was partially offset with tax benefits related to bases differences in non-U.S. jurisdictions.

Employee Benefit Plans

Employee Benefit Plans	3 Months Ended
	Mar. 31, 2018
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans The components of net periodic benefit cost, included in other operating expenses on the condensed consolidated statements of income, for the three months ended March 31, 2018 and 2017 were as follows (dollars in thousands): Pension Benefits Other Benefits Three months ended March 31, Three months ended March 31, 2018 2017 2018 2017 Service cost $ 2,654 $ 2,580 $ 636 $ 721 Interest cost 1,330 1,198 530 565 Expected return on plan assets (1,554 ) (1,285 ) — — Amortization of prior service cost (credit) 83 74 (329 ) (156 ) Amortization of prior actuarial losses 1,094 1,081 498 457 Settlements — 257 — — Net periodic benefit cost $ 3,607 $ 3,905 $ 1,335 $ 1,587 The Company made no pension contributions during the first three months of 2018 and expects to make pension contributions between $8.0 million and $10.0 million in 2018.

Reinsurance

Reinsurance	3 Months Ended
	Mar. 31, 2018
Retrocession Arrangements And Reinsurance Ceded Receivables [Abstract]
Retrocession Arrangements and Reinsurance Ceded Receivables	Reinsurance 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 March 31, 2018 and December 31, 2017 , 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 March 31, 2018 and December 31, 2017 , 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 reinsurance ceded 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 March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 Reinsurer A.M. Best Rating Amount % of Total Amount % of Total Reinsurer A A+ $ 317,136 39.1 % $ 301,478 38.6 % Reinsurer B A+ 203,137 25.1 203,898 26.1 Reinsurer C A 69,434 8.6 67,723 8.7 Reinsurer D A++ 42,967 5.3 40,592 5.2 Reinsurer E A+ 42,538 5.2 40,528 5.2 Other reinsurers 135,342 16.7 127,808 16.2 Total $ 810,554 100.0 % $ 782,027 100.0 % Included in the total reinsurance ceded receivables balance were $291.1 million and $243.8 million of claims recoverable, of which $17.6 million and $1.9 million were in excess of 90 days past due, as of March 31, 2018 and December 31, 2017 , respectively.

New Accounting Standards

New Accounting Standards	3 Months Ended
	Mar. 31, 2018
Accounting Changes and Error Corrections [Abstract]
New Accounting Standards	New Accounting Standards 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™. 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 condensed consolidated financial statements. Description Date of Adoption Effect on the financial statements or other significant matters Standards adopted: Reporting Comprehensive Income This updated guidance requires 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. December 31, 2017 The Company adopted the new guidance 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. Stock Compensation This 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. 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 consolidated financial statements. Financial Instruments - Recognition and Measurement This guidance 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. January 1, 2018 This guidance 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. Standards not yet adopted: Leases This 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. Early adoption is permitted. January 1, 2019 This new standard will be adopted by applying a modified retrospective transition approach, which includes a number of practical expedients. 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. Derivatives and Hedging This 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. Early adoption is permitted. January 1, 2019 This new guidance will be adopted by applying a modified retrospective approach to existing hedging relationships as of the date of adoption. The Company is currently evaluating the impact of this updated guidance on its consolidated financial statements. Financial Instruments - Credit Losses This guidance 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. Early adoption is permitted. January 1, 2020 This 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.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule Of Earnings Per Share Basic And Diluted By Common Class [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): Three months ended March 31, 2018 2017 Earnings: Net income (numerator for basic and diluted calculations) $ 100,230 $ 145,512 Shares: Weighted average outstanding shares (denominator for basic calculation) 64,490 64,353 Equivalent shares from outstanding stock options 1,382 1,318 Denominator for diluted calculation 65,872 65,671 Earnings per share: Basic $ 1.55 $ 2.26 Diluted $ 1.52 $ 2.22

Equity (Tables)

Equity (Tables)	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [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, 2017 79,137,758 14,685,663 64,452,095 Stock-based compensation (1) — (60,678 ) 60,678 Balance, March 31, 2018 79,137,758 14,624,985 64,512,773 Issued Held In Treasury Outstanding Balance, December 31, 2016 79,137,758 14,835,256 64,302,502 Stock-based compensation (1) — (86,049 ) 86,049 Balance, March 31, 2017 79,137,758 14,749,207 64,388,551 (1) Represents net shares issued from treasury pursuant to the Company’s equity-based compensation programs.
Components of Accumulated Other Comprehensive Income	The balance of and changes in each component of accumulated other comprehensive income (loss) (“AOCI”) for the three months ended March 31, 2018 and 2017 are as follows (dollars in thousands): Accumulated Other Comprehensive Income (Loss), Net of Income Tax Accumulated Currency Translation Adjustments Unrealized Appreciation (Depreciation) of Investments (1) Pension and Postretirement Benefits Total Balance, December 31, 2017 $ (86,350 ) $ 2,200,661 $ (50,680 ) $ 2,063,631 Other comprehensive income (loss) before reclassifications 5,696 (827,701 ) (1,910 ) (823,915 ) Amounts reclassified to AOCI — 21,274 1,346 22,620 Deferred income tax benefit (expense) (6,856 ) 172,823 93 166,060 Balance, March 31, 2018 $ (87,510 ) $ 1,567,057 $ (51,151 ) $ 1,428,396 Accumulated Other Comprehensive Income (Loss), Net of Income Tax Accumulated Currency Translation Adjustments Unrealized Appreciation (Depreciation) of Investments (1) Pension and Postretirement Benefits Total Balance, December 31, 2016 $ (172,541 ) $ 1,355,033 $ (43,163 ) $ 1,139,329 Other comprehensive income (loss) before reclassifications (50,735 ) 283,443 (27 ) 232,681 Amounts reclassified to AOCI — 5,762 1,456 7,218 Deferred income tax benefit (expense) 28,522 (86,090 ) (505 ) (58,073 ) Balance, March 31, 2017 $ (194,754 ) $ 1,558,148 $ (42,239 ) $ 1,321,155 (1) Includes cash flow hedges of $20,662 and $2,619 as of March 31, 2018 and December 31, 2017 , respectively, and $7,690 and $(2,496) as of March 31, 2017 and December 31, 2016 , respectively. See Note 5 - “Derivative Instruments” for additional information on cash flow hedges.
Reclassification Out Of Accumulated Other Comprehensive Income	The following table presents the amounts of AOCI reclassifications for the three months ended March 31, 2018 and 2017 (dollars in thousands): Amount Reclassified from AOCI Three months ended March 31, Details about AOCI Components 2018 2017 Affected Line Item in Statement of Income Net unrealized investment gains (losses): Net unrealized gains (losses) on available-for-sale securities $ (14,456 ) $ (11,857 ) Investment related gains (losses), net Cash flow hedges - Interest rate (370 ) — (1) Cash flow hedges - Currency/Interest rate 144 197 (1) Cash flow hedges - Forward bond purchase commitments — 50 (1) Deferred policy acquisition costs attributed to unrealized gains and losses (6,592 ) 5,848 (2) Total (21,274 ) (5,762 ) Provision for income taxes 4,678 3,194 Net unrealized gains (losses), net of tax $ (16,596 ) $ (2,568 ) Amortization of defined benefit plan items: Prior service cost (credit) $ 246 $ 82 (3) Actuarial gains/(losses) (1,592 ) (1,538 ) (3) Total (1,346 ) (1,456 ) Provision for income taxes 283 510 Amortization of defined benefit plans, net of tax $ (1,063 ) $ (946 ) Total reclassifications for the period $ (17,659 ) $ (3,514 ) (1) See Note 5 - “Derivative Instruments” for additional information on cash flow hedges. (2) This AOCI component is included in the computation of the deferred policy acquisition cost. See Note 8 – “Deferred Policy Acquisition Costs” of the 2017 Annual Report for additional details. (3) This AOCI component is included in the computation of the net periodic pension cost. See Note 10 – “Employee Benefit Plans” for additional detai

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2018
Investments [Abstract]
Available For Sale Securities	The following table provides information relating to investments in fixed maturity securities by sector as of March 31, 2018 (dollars in thousands): March 31, 2018: Amortized Unrealized Unrealized Estimated Fair % of Other-than- Cost Gains Losses Value Total in AOCI Available-for-sale: Corporate $ 22,890,985 $ 869,867 $ 240,383 $ 23,520,469 61.9 % $ — Canadian government 2,803,077 1,297,817 3,040 4,097,854 10.8 — RMBS 1,791,007 23,640 27,499 1,787,148 4.7 — ABS 1,727,810 16,383 9,471 1,734,722 4.6 275 CMBS 1,281,452 12,717 12,236 1,281,933 3.4 — U.S. government 1,486,262 9,266 59,414 1,436,114 3.8 — State and political subdivisions 672,064 49,465 8,016 713,513 1.9 — Other foreign government 3,261,048 133,865 21,406 3,373,507 8.9 — Total fixed maturity securities $ 35,913,705 $ 2,413,020 $ 381,465 $ 37,945,260 100.0 % $ 275 The following table provides information relating to investments in fixed maturity and equity securities by sector as of December 31, 2017 (dollars in thousands): December 31, 2017: Amortized Unrealized Unrealized Estimated Fair % of Other-than- Cost Gains Losses Value Total 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 %
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 March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Fixed maturity securities pledged as collateral $ 72,850 $ 75,384 $ 72,542 $ 75,622 Fixed maturity securities received as collateral n/a 614,423 n/a 590,417 Assets in trust held to satisfy collateral requirements 16,316,662 17,076,547 15,584,296 16,715,281
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 March 31, 2018 and December 31, 2017 (dollars in thousands). March 31, 2018 December 31, 2017 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Fixed maturity securities guaranteed or issued by: Canadian province of Quebec $ 1,106,753 $ 1,863,568 $ 1,119,337 $ 1,917,996 Canadian province of Ontario 928,384 1,247,158 939,837 1,282,944
Investments Classified By Contractual Maturity Date	The amortized cost and estimated fair value of fixed maturity securities classified as available-for-sale at March 31, 2018 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 $ 900,166 $ 905,385 Due after one year through five years 7,939,821 8,084,053 Due after five years through ten years 9,533,025 9,779,934 Due after ten years 12,740,424 14,372,085 Asset and mortgage-backed securities 4,800,269 4,803,803 Total $ 35,913,705 $ 37,945,260
Fixed Maturity Holdings Industry Types Weighted Average Credit Ratings [Table Text Block]	The tables below show the major industry types of the Company’s corporate fixed maturity holdings as of March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018: Estimated Amortized Cost Fair Value % of Total Finance $ 8,250,681 $ 8,407,037 35.8 % Industrial 12,093,034 12,437,180 52.8 Utility 2,547,270 2,676,252 11.4 Total $ 22,890,985 $ 23,520,469 100.0 % December 31, 2017: Estimated Amortized Cost 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 %
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): Three months ended March 31, 2018 2017 Balance, beginning of period $ 3,677 $ 6,013 Credit loss OTTI previously recognized on securities impaired to fair value during the period — (2,336 ) Balance, end of period $ 3,677 $ 3,677
Investments In Debt And Equity Securities Gross Unrealized Losses Disclosures	The following table presents the total gross unrealized losses for the 2,114 fixed maturity securities as of March 31, 2018 , where the estimated fair value had declined and remained below amortized cost by the indicated amount (dollars in thousands): March 31, 2018 Gross Unrealized Losses % of Total Less than 20% $ 358,873 94.1 % 20% or more for less than six months 20,232 5.3 20% or more for six months or greater 2,360 0.6 Total $ 381,465 100.0 % The following table presents the total gross unrealized losses for the 1,116 fixed maturity and equity securities at December 31, 2017 where the estimated fair value had declined and remained below amortized cost by the indicated amount (dollars in thousands): December 31, 2017 Gross % of Total Less than 20% $ 113,466 97.0 % 20% or more for less than six months 689 0.6 20% or more for six months or greater 2,838 2.4 Total $ 116,993 100.0 %
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table Text Block]	The following table presents the estimated fair values and gross unrealized losses, including other-than-temporary impairment losses reported in AOCI, for 2,114 fixed maturity securities that have estimated fair values below amortized cost as of March 31, 2018 (dollars in thousands). 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. Less than 12 months 12 months or greater Total Gross Gross Gross March 31, 2018: Estimated Unrealized Estimated Unrealized Estimated Unrealized Fair Value Losses Fair Value Losses Fair Value Losses Investment grade securities: Corporate $ 7,282,079 $ 155,541 $ 883,699 $ 46,908 $ 8,165,778 $ 202,449 Canadian government 39,192 390 109,552 2,536 148,744 2,926 RMBS 897,255 19,899 225,288 7,575 1,122,543 27,474 ABS 612,053 7,001 114,605 2,423 726,658 9,424 CMBS 538,464 8,026 103,447 4,210 641,911 12,236 U.S. government 488,095 16,856 744,844 42,558 1,232,939 59,414 State and political subdivisions 135,158 3,331 67,949 4,685 203,107 8,016 Other foreign government 746,485 15,575 191,446 5,000 937,931 20,575 Total investment grade securities 10,738,781 226,619 2,440,830 115,895 13,179,611 342,514 Below investment grade securities: Corporate 452,086 29,597 46,976 8,337 499,062 37,934 Canadian government 1,900 114 — — 1,900 114 RMBS — — 1,272 25 1,272 25 ABS — — 1,173 47 1,173 47 Other foreign government 57,385 662 12,045 169 69,430 831 Total below investment grade securities 511,371 30,373 61,466 8,578 572,837 38,951 Total fixed maturity securities $ 11,250,152 $ 256,992 $ 2,502,296 $ 124,473 $ 13,752,448 $ 381,465 The following table presents the estimated fair values and gross unrealized losses, including other-than-temporary impairment losses reported in AOCI, for 1,116 fixed maturity and equity securities that have estimated fair values below amortized cost as of December 31, 2017 (dollars in thousands): Less than 12 months 12 months or greater Total Gross Gross Gross December 31, 2017: Estimated Unrealized Estimated Unrealized Estimated Unrealized Fair Value Losses Fair Value Losses Fair Value Losses 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
Investment Income	Major categories of investment income, net of related expenses, consist of the following (dollars in thousands): Three months ended March 31, 2018 2017 Fixed maturity securities available-for-sale $ 369,203 $ 324,500 Equity securities 1,682 1,359 Mortgage loans on real estate 50,199 44,347 Policy loans 14,780 15,272 Funds withheld at interest 75,445 127,578 Short-term investments and cash and cash equivalents 3,245 1,510 Other 23,828 18,468 Investment income 538,382 533,034 Investment expense (22,053 ) (18,670 ) Investment income, net of related expenses $ 516,329 $ 514,364
Gain Loss On Investments	Investment related gains (losses), net consist of the following (dollars in thousands): Three months ended March 31, 2018 2017 Fixed maturity securities available for sale: Other-than-temporary impairment losses on fixed maturity securities recognized in earnings $ — $ (17,189 ) Gain on investment activity 10,966 17,893 Loss on investment activity (20,380 ) (8,687 ) Equity securities: Gain on investment activity 28 — Loss on investment activity (950 ) (3,876 ) Change in unrealized gains (losses) recognized in earnings (4,137 ) — Other impairment losses and change in mortgage loan provision (312 ) (99 ) Derivatives and other, net 14,315 72,481 Total investment related gains (losses), net $ (470 ) $ 60,523
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 and repurchased/reverse repurchased securities pledged and received as of March 31, 2018 and December 31, 2017 (dollars in thousands). March 31, 2018 December 31, 2017 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Borrowed securities $ 353,875 $ 370,760 $ 358,875 $ 377,820 Securities lending: Securities loaned 117,449 118,617 117,246 121,551 Securities received n/a 128,000 n/a 128,000 Repurchase program/reverse repurchase program: Securities pledged 403,135 411,988 413,819 428,344 Securities received n/a 404,871 n/a 417,550
Schedule of Underlying Assets of Repurchase Agreements when Amount of Repurchase Agreements Exceeds 10 Percent of Assets [Table Text Block]	The following table presents information on the Company’s securities lending and repurchase transactions as of March 31, 2018 and December 31, 2017 (dollars in thousands). Collateral associated with certain borrowed securities is not included within the table, as the collateral pledged to each counterparty is the right to reinsurance treaty cash flows. March 31, 2018 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total Securities lending transactions: Corporate $ — $ — $ — $ 118,617 $ 118,617 Total $ — $ — $ — $ 118,617 $ 118,617 Repurchase transactions: Corporate $ — $ — $ — $ 171,678 $ 171,678 RMBS — — — — — U.S. government — — — 219,509 219,509 Foreign government — — — 19,670 19,670 Other 1,131 — — — 1,131 Total 1,131 — — 410,857 411,988 Total borrowings $ 1,131 $ — $ — $ 529,474 $ 530,605 Gross amount of recognized liabilities for securities lending and repurchase transactions in preceding table $ 563,587 Amounts related to agreements not included in offsetting disclosure $ 32,982 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 transactions: 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 borrowings $ 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
Disclosure Of Real Estate Holdings By Property Type [Table Text Block]	he distribution of mortgage loans by property type is as follows as of March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 Property type: Carrying Value % of Total Carrying Value % of Total Office building $ 1,518,170 34.1 % $ 1,487,392 33.6 % Retail 1,236,933 27.8 1,270,676 28.8 Industrial 964,685 21.7 938,612 21.3 Apartment 497,699 11.2 510,052 11.6 Other commercial 232,804 5.2 206,439 4.7 Recorded investment 4,450,291 100.0 % $ 4,413,171 100.0 % Unamortized balance of loan origination fees and expenses (3,433 ) (3,254 ) Valuation allowances (8,864 ) (9,384 ) Total mortgage loans on real estate $ 4,437,994 $ 4,400,533
Mortgage Loans Classified By Contractual Maturity Date [Table Text Block]	he maturities of the mortgage loans as of March 31, 2018 and December 31, 2017 are as follows (dollars in thousands): March 31, 2018 December 31, 2017 Recorded Investment % of Total Recorded Investment % of Total Due within five years $ 1,130,108 25.4 % $ 1,091,066 24.8 % Due after five years through ten years 2,492,588 56.0 2,516,872 57.0 Due after ten years 827,595 18.6 805,233 18.2 Total $ 4,450,291 100.0 % $ 4,413,171 100.0 %
Mortgage Loan Internal Credit Risk Grade [Table Text Block]	The following tables set forth certain key credit quality indicators of the Company’s recorded investment in mortgage loans as of March 31, 2018 and December 31, 2017 (dollars in thousands): Recorded Investment Debt Service Ratios Construction loans >1.20x 1.00x - 1.20x <1.00x Total % of Total March 31, 2018: Loan-to-Value Ratio 0% - 59.99% $ 2,154,344 $ 79,738 $ 6,855 $ 12,279 $ 2,253,216 50.6 % 60% - 69.99% 1,520,008 29,795 68,070 — 1,617,873 36.4 70% - 79.99% 360,183 27,682 30,904 — 418,769 9.4 Greater than 80% 125,660 30,497 4,276 — 160,433 3.6 Total $ 4,160,195 $ 167,712 $ 110,105 $ 12,279 $ 4,450,291 100.0 % 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 %
Past Due Financing Receivables [Table Text Block]	The age analysis of the Company’s past due recorded investments in mortgage loans as of March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 31-60 days past due $ 17,102 $ 17,100 61-90 days past due — 2,056 Greater than 90 days 2,056 — Total past due 19,158 19,156 Current 4,431,133 4,394,015 Total $ 4,450,291 $ 4,413,171
Recorded Investment And Allowance For Credit Losses	he following table presents the recorded investment in mortgage loans, by method of measuring impairment, and the related valuation allowances as of March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 Mortgage loans: Individually measured for impairment $ 23,423 $ 5,858 Collectively measured for impairment 4,426,868 4,407,313 Recorded investment $ 4,450,291 $ 4,413,171 Valuation allowances: Individually measured for impairment $ — $ — Collectively measured for impairment 8,864 9,384 Total valuation allowances $ 8,864 $ 9,384
Allowance For Mortgage Loan And Lease Losses Provision For Loss Net	nformation regarding the Company’s loan valuation allowances for mortgage loans for the three months ended March 31, 2018 and 2017 is as follows (dollars in thousands): Three months ended March 31, 2018 2017 Balance, beginning of period $ 9,384 $ 7,685 Provision (release) (516 ) 101 Translation adjustment (4 ) — Balance, end of period $ 8,864 $ 7,786
Impaired Financing Receivables Table	Information regarding the portion of the Company’s mortgage loans that were impaired as of March 31, 2018 and December 31, 2017 is as follows (dollars in thousands): Unpaid Principal Balance Recorded Investment Related Allowance Carrying Value March 31, 2018: Impaired mortgage loans with no valuation allowance recorded $ — $ 23,423 $ — $ 23,423 Impaired mortgage loans with valuation allowance recorded — — — — Total impaired mortgage loans $ — $ 23,423 $ — $ 23,423 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 The Company’s average investment balance of impaired mortgage loans and the related interest income are reflected in the table below for the periods indicated (dollars in thousands): Three months ended March 31, 2018 2017 Average (1) Interest Income Average (1) Interest Income Impaired mortgage loans with no valuation allowance recorded $ 14,640 $ 56 $ 2,157 $ 33 Impaired mortgage loans with valuation allowance recorded — — — — Total impaired mortgage loans $ 14,640 $ 56 $ 2,157 $ 33 (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 Invested Assets [Table Text Block]	arrying values of these assets as of March 31, 2018 and December 31, 2017 are as follows (dollars in thousands): March 31, 2018 December 31, 2017 Limited partnership interests and real estate joint ventures 805,613 781,124 Equity release mortgages 261,837 219,940 Derivatives 132,195 137,613 FVO contractholder-directed unit-linked investments 221,512 218,541 Other 90,990 148,114 Total other invested assets $ 1,512,147 $ 1,505,332

Derivative Instruments (Tables)

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule Of Derivative Instruments In Statement Of Financial Position 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 March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 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 $ 1,021,739 $ 47,303 $ 152 $ 996,204 $ 59,809 $ 2,372 Financial futures 388,874 — — 412,438 — — Foreign currency forwards 6,012 48 4 6,030 — 28 Consumer price index swaps 218,237 127 427 221,932 — 2,160 Credit default swaps 933,200 7,279 1,058 961,200 8,319 1,651 Equity options 639,801 33,958 — 632,251 23,271 — Longevity swaps 985,920 44,011 — 960,400 40,659 — Mortality swaps — — 1,683 — — 1,683 Synthetic guaranteed investment contracts 10,866,171 — — 10,052,576 — — Embedded derivatives in: Modified coinsurance or funds withheld arrangements — 135,805 — — 122,194 — Indexed annuity products — — 827,109 — — 861,758 Variable annuity products — — 137,686 — — 152,470 Total non-hedging derivatives 15,059,954 268,531 968,119 14,243,031 254,252 1,022,122 Derivatives designated as hedging instruments: Interest rate swaps 435,000 (1,119 ) 16,972 435,000 — 20,389 Foreign currency swaps 598,575 56,403 5,461 672,921 65,207 8,496 Foreign currency forwards 698,241 7,458 225 553,175 1,265 7,720 Total hedging derivatives 1,731,816 62,742 22,658 1,661,096 66,472 36,605 Total derivatives $ 16,791,770 $ 331,273 $ 990,777 $ 15,904,127 $ 320,724 $ 1,058,727
Offsetting Assets [Table Text Block]	The following table provides information relating to the Company’s derivative instruments as of March 31, 2018 and December 31, 2017 (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 March 31, 2018: Derivative assets $ 195,468 $ (19,262 ) $ 176,206 $ — $ (188,407 ) $ (12,201 ) Derivative liabilities 25,982 (19,262 ) 6,720 (57,456 ) (3,470 ) (54,206 ) 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 ) (1) Includes initial margin posted to a central clearing partner.
Offsetting Liabilities [Table Text Block]	The following table provides information relating to the Company’s derivative instruments as of March 31, 2018 and December 31, 2017 (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 March 31, 2018: Derivative assets $ 195,468 $ (19,262 ) $ 176,206 $ — $ (188,407 ) $ (12,201 ) Derivative liabilities 25,982 (19,262 ) 6,720 (57,456 ) (3,470 ) (54,206 ) 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 ) (1) Includes initial margin posted to a central clearing partner.
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 March 31, 2018 and 2017, 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 three months ended March 31, 2018: Foreign currency swaps Foreign-denominated fixed maturity securities $ (1,891 ) $ 1,891 $ — For the three months ended March 31, 2017: Foreign currency swaps Foreign-denominated fixed maturity securities $ 6,536 $ (6,536 ) $ —
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 condensed consolidated income statement classification where the gain or loss is recognized related to cash flow hedges for the three months ended March 31, 2018 and 2017 (dollars in thousands): Three months ended March 31, 2018 2017 Balance beginning of period $ 2,619 $ (2,496 ) Gains (losses) deferred in other comprehensive income (loss) on the effective portion of cash flow hedges 17,817 10,433 Amounts reclassified to investment income (144 ) (247 ) Amounts reclassified to interest expense 370 — Balance end of period $ 20,662 $ 7,690
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 condensed consolidated statements of income and the condensed consolidated statements of comprehensive income for the three months ended March 31, 2018 and 2017 (dollars in thousands): Effective Portion Derivative Type Gain (Loss) Deferred in OCI Gain (Loss) Reclassified into Income from OCI Investment Income Interest Expense For the three months ended March 31, 2018: Interest rate $ 14,986 $ — $ (370 ) Currency/Interest rate 2,831 144 — Forward bond purchase commitments — — — Total $ 17,817 $ 144 $ (370 ) For the three months ended March 31, 2017: Interest rate $ 2,216 $ — $ — Currency/Interest rate 8,217 197 — Forward bond purchase commitments — 50 — Total $ 10,433 $ 247 $ —
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 three months ended March 31, 2018 and 2017 (dollars in thousands): Derivative Gains (Losses) Deferred in AOCI For the three months ended March 31, Type of NIFO Hedge (1) (2) 2018 2017 Foreign currency swaps $ 8,805 $ (7,606 ) Foreign currency forwards 12,236 — (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.
Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block]	A summary of the effect of non-hedging derivatives, including embedded derivatives, on the Company’s condensed consolidated statements of income for the three months ended March 31, 2018 and 2017 is as follows (dollars in thousands): Gain (Loss) for the three months ended March 31, Type of Non-hedging Derivative Income Statement Location of Gain (Loss) 2018 2017 Interest rate swaps Investment related gains (losses), net $ (26,571 ) $ (2,612 ) Financial futures Investment related gains (losses), net 129 (12,775 ) Foreign currency forwards Investment related gains (losses), net 323 904 CPI swaps Investment related gains (losses), net 2,186 (5 ) Credit default swaps Investment related gains (losses), net (402 ) 7,358 Equity options Investment related gains (losses), net 2,593 (17,189 ) Longevity swaps Other revenues 2,267 1,865 Mortality swaps Other revenues — (395 ) Subtotal (19,475 ) (22,849 ) Embedded derivatives in: Modified coinsurance or funds withheld arrangements Investment related gains (losses), net 13,611 68,702 Indexed annuity products Interest credited 25,351 (16,402 ) Variable annuity products Investment related gains (losses), net 14,785 22,363 Total non-hedging derivatives $ 34,272 $ 51,814
Disclosure Of Credit Derivatives	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 March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 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 Value of Credit Default Swaps Maximum Amount of Future Payments under Credit Default Swaps (2) Weighted Average Years to Maturity (3) AAA/AA+/AA/AA-/A+/A/A- Single name credit default swaps $ 2,761 $ 152,000 3.0 $ 3,128 $ 162,000 2.9 Subtotal 2,761 152,000 3.0 3,128 162,000 2.9 BBB+/BBB/BBB- Single name credit default swaps 4,203 333,700 2.8 4,469 361,700 2.9 Credit default swaps referencing indices 156 422,600 3.7 (55 ) 422,600 4.0 Subtotal 4,359 756,300 3.3 4,414 784,300 3.5 BB+/BB/BB- Single name credit default swaps (25 ) 15,000 1.5 30 5,000 1.5 Subtotal (25 ) 15,000 1.5 30 5,000 1.5 Total $ 7,095 $ 923,300 3.2 $ 7,572 $ 951,300 3.4 (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	The related gains (losses) and the effect on net income after amortization of deferred acquisition costs (“DAC”) and income taxes for the three months ended March 31, 2018 and 2017 are reflected in the following table (dollars in thousands): Three months ended March 31, 2018 2017 Embedded derivatives in modco or funds withheld arrangements included in investment related gains $ 13,611 $ 68,702 After the associated amortization of DAC and taxes, the related amounts included in net income 6,850 25,844 Embedded derivatives in variable annuity contracts included in investment related gains 14,785 22,363 After the associated amortization of DAC and taxes, the related amounts included in net income 11,126 28,836 Amounts related to embedded derivatives in equity-indexed annuities included in benefits and expenses 25,351 (16,402 ) After the associated amortization of DAC and taxes, the related amounts included in net income 6,537 (21,396 )
Credit Risk	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 March 31, 2018 and December 31, 2017 are reflected in the following table (dollars in thousands): March 31, 2018 December 31, 2017 Estimated fair value of derivatives in net asset position $ 171,169 $ 155,714 Cash provided as collateral (1) 3,470 22,221 Securities pledged to counterparties as collateral (2) 57,456 58,156 Cash pledged from counterparties as collateral (3) (188,407 ) (185,900 ) Securities pledged from counterparties as collateral (4) — (862 ) Initial margin for cleared derivatives (2) (57,456 ) (58,156 ) Net amount after application of master netting agreements and collateral $ (13,768 ) $ (8,827 ) Margin account related to exchange-traded futures (5) $ 7,382 $ 6,538 (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 securities. (5) Included in other assets.

Fair Value of Assets and Liab25

Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 and December 31, 2017 are summarized below (dollars in thousands): March 31, 2018: Fair Value Measurements Using: Total Level 1 Level 2 Level 3 Assets: Fixed maturity securities – available-for-sale: Corporate $ 23,520,469 $ — $ 22,221,205 $ 1,299,264 Canadian government 4,097,854 — 3,525,107 572,747 RMBS 1,787,148 — 1,666,534 120,614 ABS 1,734,722 — 1,604,016 130,706 CMBS 1,281,933 — 1,280,049 1,884 U.S. government 1,436,114 1,313,806 101,255 21,053 State and political subdivisions 713,513 — 671,637 41,876 Other foreign government 3,373,507 — 3,368,503 5,004 Total fixed maturity securities – available-for-sale 37,945,260 1,313,806 34,438,306 2,193,148 Equity securities 103,983 67,831 — 36,152 Funds withheld at interest – embedded derivatives 135,805 — — 135,805 Cash equivalents 538,761 538,761 — — Short-term investments 58,499 67 55,215 3,217 Other invested assets: Derivatives: Interest rate swaps 40,812 — 40,812 — Foreign currency forwards 6,932 — 6,932 — CPI swaps (99 ) — (99 ) — Credit default swaps 5,465 — 5,465 — Equity options 27,140 — 27,140 — Foreign currency swaps 51,945 — 51,945 — FVO contractholder-directed unit-linked investments 221,512 221,043 469 — Total other invested assets 353,707 221,043 132,664 — Other assets - longevity swaps 44,011 — — 44,011 Total $ 39,180,026 $ 2,141,508 $ 34,626,185 $ 2,412,333 Liabilities: Interest sensitive contract liabilities – embedded derivatives $ 964,795 $ — $ — $ 964,795 Other liabilities: Derivatives: Interest rate swaps 11,752 — 11,752 — Foreign currency forwards (345 ) — (345 ) — CPI swaps 201 — 201 — Credit default swaps (756 ) — (756 ) — Equity options (6,818 ) — (6,818 ) — Foreign currency swaps 1,003 — 1,003 — Mortality swaps 1,683 — — 1,683 Total $ 971,515 $ — $ 5,037 $ 966,478 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 Equity securities: Non-redeemable preferred stock 39,806 39,806 — — Other equity securities 60,346 60,346 — — 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: 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 356,154 217,618 138,536 — 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
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Level Transfers [Table Text Block]	The following tables present the transfers between Level 1 and Level 2 during the three months ended March 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 $ — $ 38,675
Fair Value Unobservable Input Measurements [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 March 31, 2018 and December 31, 2017 (dollars in thousands): Estimated Fair Value Valuation Technique Unobservable Inputs Range (Weighted Average) March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 Assets: Corporate $183,680 $173,579 Market comparable securities Liquidity premium 0-2% (1%) 0-2% (1%) EBITDA Multiple 5.9X - 7.5X (6.6X) — U.S. government 21,053 22,511 Market comparable securities Liquidity premium 0-1% (1%) 0-1% (1%) State and political subdivisions 4,452 4,616 Market comparable securities Liquidity premium 1 % 1 % Equity securities 25,987 — Market comparable securities Liquidity premium 3% — EBITDA Multiple 6.9X - 13.1X (8.0X) — Funds withheld at interest- embedded derivatives 135,805 122,194 Total return swap Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (9%) Withdrawal 0-5% (3%) 0-5% (3%) CVA 0-5% (1%) 0-5% (1%) Crediting rate 2-4% (2%) 2-4% (2%) Longevity swaps 44,011 40,659 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 827,109 861,758 Discounted cash flow Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (9%) Withdrawal 0-5% (3%) 0-5% (3%) Option budget projection 2-4% (2%) 2-4% (2%) Interest sensitive contract liabilities- embedded derivatives- variable annuities 137,686 152,470 Discounted cash flow Mortality 0-100% (1%) 0-100% (1%) Lapse 0-25% (5%) 0-25% (5%) Withdrawal 0-7% (4%) 0-7% (3%) CVA 0-5% (1%) 0-5% (1%) Long-term volatility 0-27% (13%) 0-27% (8%) Mortality swaps 1,683 1,683 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 March 31, 2018 and December 31, 2017 (dollars in thousands): Estimated Fair Value Valuation Technique Unobservable Inputs Range (Weighted Average) March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 Assets: Corporate $183,680 $173,579 Market comparable securities Liquidity premium 0-2% (1%) 0-2% (1%) EBITDA Multiple 5.9X - 7.5X (6.6X) — U.S. government 21,053 22,511 Market comparable securities Liquidity premium 0-1% (1%) 0-1% (1%) State and political subdivisions 4,452 4,616 Market comparable securities Liquidity premium 1 % 1 % Equity securities 25,987 — Market comparable securities Liquidity premium 3% — EBITDA Multiple 6.9X - 13.1X (8.0X) — Funds withheld at interest- embedded derivatives 135,805 122,194 Total return swap Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (9%) Withdrawal 0-5% (3%) 0-5% (3%) CVA 0-5% (1%) 0-5% (1%) Crediting rate 2-4% (2%) 2-4% (2%) Longevity swaps 44,011 40,659 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 827,109 861,758 Discounted cash flow Mortality 0-100% (2%) 0-100% (2%) Lapse 0-35% (9%) 0-35% (9%) Withdrawal 0-5% (3%) 0-5% (3%) Option budget projection 2-4% (2%) 2-4% (2%) Interest sensitive contract liabilities- embedded derivatives- variable annuities 137,686 152,470 Discounted cash flow Mortality 0-100% (1%) 0-100% (1%) Lapse 0-25% (5%) 0-25% (5%) Withdrawal 0-7% (4%) 0-7% (3%) CVA 0-5% (1%) 0-5% (1%) Long-term volatility 0-27% (13%) 0-27% (8%) Mortality swaps 1,683 1,683 Discounted cash flow Mortality 0-100% (1%) 0-100% (1%)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	For the three months ended March 31, 2018: Fixed maturity securities - available-for-sale Corporate Canadian government RMBS ABS Fair value, beginning of period $ 1,337,272 $ 593,942 $ 107,882 $ 123,474 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (361 ) 3,444 (92 ) 106 Investment related gains (losses), net — — — 2 Included in other comprehensive income (32,852 ) (24,639 ) (1,110 ) 853 Purchases (1) 100,170 — 20,916 11,000 Sales (1) (6,180 ) — — — Settlements (1) (75,146 ) — (2,963 ) (2,739 ) Transfers into Level 3 7,166 — — — Transfers out of Level 3 (30,805 ) — (4,019 ) (1,990 ) Fair value, end of period $ 1,299,264 $ 572,747 $ 120,614 $ 130,706 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 $ (361 ) $ 3,444 $ (92 ) $ 106 For the three months ended March 31, 2018 (continued): Fixed maturity securities - available-for-sale CMBS U.S. government State Other foreign government Fair value, beginning of period $ 3,234 $ 22,511 $ 41,203 $ 5,092 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses — (110 ) 8 — Included in other comprehensive income (47 ) (340 ) 700 (88 ) Purchases (1) — 96 — — Settlements (1) (1 ) (1,104 ) (35 ) — Transfers out of Level 3 (1,302 ) — — — Fair value, end of period $ 1,884 $ 21,053 $ 41,876 $ 5,004 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 $ — $ (110 ) $ 8 $ — For the three months ended March 31, 2018 (continued): Equity securities Funds withheld at interest- embedded derivatives Short-term Investments Other assets - longevity swaps Interest sensitive contract liabilities embedded derivatives Other liabilities - mortality swaps Fair value, beginning of period $ — $ 122,194 $ 3,096 $ 40,659 $ (1,014,229 ) $ (1,683 ) Total gains/losses (realized/unrealized) Included in earnings, net: Investment related gains (losses), net (2,677 ) 13,611 — — 14,785 — Interest credited — — — — 25,351 — Included in other comprehensive income — — (25 ) 1,085 — — Other revenues — — — 2,267 — — Purchases (1) — — 146 — (8,508 ) — Sales (1) (28 ) — — — — — Settlements (1) (48 ) — — — 17,807 — Transfers into Level 3 38,905 — — — — — Fair value, end of period $ 36,152 $ 135,805 $ 3,217 $ 44,011 $ (964,794 ) $ (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 income, net of related expenses $ — $ — $ — $ — $ — $ — Investment related gains (losses), net (2,705 ) 13,611 — — 12,901 — Other revenues — — — 2,267 — — Interest credited — — — — 7,544 — For the three months ended March 31, 2017: Fixed maturity securities - available-for-sale Corporate Canadian governments RMBS ABS CMBS U.S. government Fair value, beginning of period $ 1,272,253 $ 475,965 $ 160,291 $ 219,280 $ 21,145 $ 24,488 Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (423 ) 3,070 (245 ) 1,018 709 (117 ) Investment related gains (losses), net (1,231 ) — 365 — (595 ) — Included in other comprehensive income 4,948 4,525 650 5,767 (83 ) 52 Purchases (1) 45,914 — 16,499 10,849 — 104 Sales (1) — — (10,604 ) — (3,720 ) — Settlements (1) (71,470 ) — (6,784 ) (18,154 ) (5,401 ) (1,053 ) Transfers into Level 3 13,934 — 77 35,258 — — Transfers out of Level 3 — — (16,819 ) (45,582 ) (10,132 ) — Fair value, end of period $ 1,263,925 $ 483,560 $ 143,430 $ 208,436 $ 1,923 $ 23,474 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 $ (423 ) $ 3,070 $ (91 ) $ 161 $ — $ (117 ) Investment related gains (losses), net (1,293 ) — (346 ) — — — For the three months ended March 31, 2017 (continued): Fixed maturity securities available-for-sale State Other foreign government Funds withheld at interest- embedded derivatives Short-term Investments Other assets - longevity swaps Interest sensitive contract liabilities embedded derivatives Other liabilities - mortality swaps Fair value, beginning of period $ 41,666 $ 12,869 $ (22,529 ) $ 3,346 $ 26,958 $ (990,308 ) $ (2,462 ) Total gains/losses (realized/unrealized) Included in earnings, net: Investment income, net of related expenses (88 ) — — — — — — Investment related gains (losses), net — — 68,702 — — 22,362 — Interest credited — — — — — (16,402 ) — Included in other comprehensive income (843 ) (191 ) — 33 347 — — Other revenues — — — — 1,865 — (395 ) Purchases (1) — — — 32 — (6,393 ) — Settlements (1) (33 ) (334 ) — (135 ) — 17,811 — Transfers out of Level 3 (6,844 ) — — — — — — Fair value, end of period $ 33,858 $ 12,344 $ 46,173 $ 3,276 $ 29,170 $ (972,930 ) $ (2,857 ) 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 $ (88 ) $ — $ — $ — $ — $ — $ — Investment related gains (losses), net — — 68,702 — — 20,300 — Other revenues — — — — 1,865 — (395 ) Interest credited — — — — — (34,214 ) — (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.
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 March 31, 2018 and December 31, 2017 (dollars in thousands). For additional information regarding the methods and significant assumptions used by the Company to estimate these fair values, see Note 6 in the Notes to Consolidated Financial Statements included in the Company’s 2017 Annual Report. 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. March 31, 2018: Carrying Value (1) Estimated Fair Value Fair Value Measurement Using: Level 1 Level 2 Level 3 NAV Assets: Mortgage loans on real estate $ 4,437,994 $ 4,411,472 $ — $ — $ 4,411,472 $ — Policy loans 1,346,930 1,346,930 — 1,346,930 — — Funds withheld at interest 5,865,791 6,098,479 — — 6,098,479 — Cash and cash equivalents 971,646 971,646 971,646 — — — Short-term investments 71,931 71,931 71,931 — — — Other invested assets 690,200 710,009 10,165 68,903 283,205 347,736 Accrued investment income 408,338 408,338 — 408,338 — — Liabilities: Interest-sensitive contract liabilities $ 13,169,951 $ 13,151,162 $ — $ — $ 13,151,162 $ — Long-term debt 2,788,240 2,916,200 — — 2,916,200 — Collateral finance and securitization notes 753,393 692,696 — — 692,696 — December 31, 2017: 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 651,792 679,377 28,540 67,778 247,934 335,125 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 — (1)

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Reconciliation Of Revenue From Segments To Consolidated Text Block	Information related to revenues, income (loss) before income taxes and total assets of the Company for each reportable segment are summarized below (dollars in thousands): Three months ended March 31, Revenues: 2018 2017 U.S. and Latin America: Traditional $ 1,489,694 $ 1,488,503 Financial Solutions 213,352 298,846 Total 1,703,046 1,787,349 Canada: Traditional 302,319 264,275 Financial Solutions 12,777 11,807 Total 315,096 276,082 Europe, Middle East and Africa: Traditional 393,782 318,086 Financial Solutions 88,143 79,989 Total 481,925 398,075 Asia Pacific: Traditional 614,539 505,230 Financial Solutions 19,846 20,452 Total 634,385 525,682 Corporate and Other 39,255 21,552 Total $ 3,173,707 $ 3,008,740
Reconciliation Of Operating Profit Loss From Segments To Consolidated Text Block	Three months ended March 31, Income (loss) before income taxes: 2018 2017 U.S. and Latin America: Traditional $ 2,892 $ 29,960 Financial Solutions 67,421 103,586 Total 70,313 133,546 Canada: Traditional 23,707 19,328 Financial Solutions 3,191 3,592 Total 26,898 22,920 Europe, Middle East and Africa: Traditional 15,421 13,976 Financial Solutions 39,164 31,918 Total 54,585 45,894 Asia Pacific: Traditional 22,887 41,688 Financial Solutions 4,021 5,872 Total 26,908 47,560 Corporate and Other (40,779 ) (42,076 ) Total $ 137,925 $ 207,844
Reconciliation Of Assets From Segment To Consolidated Text Block	Assets: March 31, 2018 December 31, 2017 U.S. and Latin America: Traditional $ 18,839,888 $ 18,603,423 Financial Solutions 16,349,148 15,959,206 Total 35,189,036 34,562,629 Canada: Traditional 4,234,253 4,161,452 Financial Solutions 126,747 126,372 Total 4,361,000 4,287,824 Europe, Middle East and Africa: Traditional 3,385,127 3,099,495 Financial Solutions 5,279,499 5,274,993 Total 8,664,626 8,374,488 Asia Pacific: Traditional 5,095,054 4,915,442 Financial Solutions 1,175,002 1,198,585 Total 6,270,056 6,114,027 Corporate and Other 6,470,105 7,175,850 Total $ 60,954,823 $ 60,514,818

Commitments, Contingencies an27

Commitments, Contingencies and Guarantees (Tables)	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 and December 31, 2017 are presented in the following table (dollars in thousands): March 31, 2018 December 31, 2017 Limited partnership interests and joint ventures $ 482,149 $ 485,197 Commercial mortgage loans 67,837 40,815 Bank loans and private placements 96,808 60,472 Equity release mortgages 132,523 153,937
Other Commitments [Table Text Block]	The following table presents the maximum potential obligation for these commitments as of March 31, 2018 (dollars in millions): Commitment Period Maximum Potential Obligation 2023 $ 500.0 2033 450.0 2034 2,000.0 2035 1,314.2 2036 1,932.0 2037 6,750.0 2038 800.0
Schedule of Guarantor Obligations [Table Text Block]	RGA’s guarantees issued as of March 31, 2018 and December 31, 2017 are reflected in the following table (dollars in thousands): March 31, 2018 December 31, 2017 Treaty guarantees $ 949,443 $ 1,047,449 Treaty guarantees, net of assets in trust 832,487 926,393 Securities borrowing and repurchase arrangements 291,325 294,325 Financing arrangements 77,858 86,183 Lease obligations 1,465 1,662

Income Tax (Tables)

Income Tax (Tables)	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	for the three months ended March 31, 2018 and 2017 , respectively (dollars in thousands): Three months ended March 31, 2018 2017 Tax provision at U.S. statutory rate $ 28,964 $ 72,745 Increase (decrease) in income taxes resulting from: U.S. Tax Reform provisional adjustments 775 — Foreign tax rate differing from U.S. tax rate 1,432 (6,153 ) Differences in tax bases in foreign jurisdictions (5,760 ) (3,383 ) Deferred tax valuation allowance 7,947 1,182 Amounts related to tax audit contingencies 835 611 Corporate rate changes 111 (1,237 ) Subpart F 658 186 Foreign tax credits (572 ) (126 ) Global intangible low-taxed income, net of credit 4,409 — Return to provision adjustments — 229 Equity compensation excess benefit (1,114 ) (1,856 ) Other, net 10 134 Total provision for income taxes $ 37,695 $ 62,332 Effective tax rate 27.3 % 30.0 %

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2018
Retirement Benefits [Abstract]
Schedule Of Defined Benefit Plans Disclosures Text Block	The components of net periodic benefit cost, included in other operating expenses on the condensed consolidated statements of income, for the three months ended March 31, 2018 and 2017 were as follows (dollars in thousands): Pension Benefits Other Benefits Three months ended March 31, Three months ended March 31, 2018 2017 2018 2017 Service cost $ 2,654 $ 2,580 $ 636 $ 721 Interest cost 1,330 1,198 530 565 Expected return on plan assets (1,554 ) (1,285 ) — — Amortization of prior service cost (credit) 83 74 (329 ) (156 ) Amortization of prior actuarial losses 1,094 1,081 498 457 Settlements — 257 — — Net periodic benefit cost $ 3,607 $ 3,905 $ 1,335 $ 1,587

Reinsurance (Tables)

Reinsurance (Tables)	3 Months Ended
	Mar. 31, 2018
Retrocession Arrangements And Reinsurance Ceded Receivables [Abstract]
Ceded Credit Risk [Table Text Block]	The following table presents information for the Company’s reinsurance ceded 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 March 31, 2018 and December 31, 2017 (dollars in thousands): March 31, 2018 December 31, 2017 Reinsurer A.M. Best Rating Amount % of Total Amount % of Total Reinsurer A A+ $ 317,136 39.1 % $ 301,478 38.6 % Reinsurer B A+ 203,137 25.1 203,898 26.1 Reinsurer C A 69,434 8.6 67,723 8.7 Reinsurer D A++ 42,967 5.3 40,592 5.2 Reinsurer E A+ 42,538 5.2 40,528 5.2 Other reinsurers 135,342 16.7 127,808 16.2 Total $ 810,554 100.0 % $ 782,027 100.0 %

Earnings Per Share (Reconciliat

Earnings Per Share (Reconciliation of the Numerators and Denominators of the Basic and Diluted Per Shares) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Net income (numerator for basic and diluted calculations)	$ 100,230	$ 145,512
Shares:
Weighted average outstanding shares (denominator for basic calculation)	64,490	64,353
Equivalent shares from outstanding stock options	1,382	1,318
Denominator for diluted calculation	65,872	65,671
Earnings Per Share:
Basic earnings per share	$ 1.55	$ 2.26
Diluted earnings per share	$ 1.52	$ 2.22

Earnings Per Share (Narrative)

Earnings Per Share (Narrative) (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
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	0.2
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	0.2	0.5

Equity (Common Stock Changes In

Equity (Common Stock Changes In Number of Shares Issued, Held In Treasury and Outstanding) (Details) - shares		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Common Stock, Shares, Issued		79,137,758		79,137,758
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
Common Stock Held In Treasury [Member]
Class of Stock [Line Items]
Common Stock, Shares, Issued		14,624,985	14,749,207	14,685,663	14,835,256
Stock Based Compensation Shares	[1]	(60,678)	(86,049)
Common Stock Outstanding [Member]
Class of Stock [Line Items]
Common Stock, Shares, Issued		64,512,773	64,388,551	64,452,095	64,302,502
Stock Based Compensation Shares	[1]	60,678	86,049
[1]	Represents net shares issued from treasury pursuant to the Company’s equity-based compensation programs.

Equity (Balance of and Changes

Equity (Balance of and Changes in Each Component of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Balance, Beginning of Period		$ 2,063,631	$ 1,139,329
Other Comprehensive Income (Loss), before Reclassifications, before Tax		(823,915)	232,681
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		22,620	7,218
Other Comprehensive Income (Loss), Tax		(166,060)	58,073
Balance, End of Period		1,428,396	1,321,155
Accumulated Translation Adjustment [Member]
Balance, Beginning of Period		(86,350)	(172,541)
Other Comprehensive Income (Loss), before Reclassifications, before Tax		5,696	(50,735)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		0	0
Other Comprehensive Income (Loss), Tax		(6,856)	28,522
Balance, End of Period		(87,510)	(194,754)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Balance, Beginning of Period	[1]	2,200,661	1,355,033
Other Comprehensive Income (Loss), before Reclassifications, before Tax	[1]	(827,701)	283,443
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1]	21,274	5,762
Other Comprehensive Income (Loss), Tax	[1]	(172,823)	86,090
Balance, End of Period	[1]	1,567,057	1,558,148
Accumulated Defined Benefit Plans Adjustment [Member]
Balance, Beginning of Period		(50,680)	(43,163)
Other Comprehensive Income (Loss), before Reclassifications, before Tax		(1,910)	(27)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		1,346	1,456
Other Comprehensive Income (Loss), Tax		(93)	505
Balance, End of Period		$ (51,151)	$ (42,239)
[1]	Includes cash flow hedges of $20,662 and $2,619 as of March 31, 2018 and December 31, 2017, respectively, and $7,690 and $(2,496) as of March 31, 2017 and December 31, 2016, respectively. See Note 5 - “Derivative Instruments” for additional information on cash flow hedges.

Equity (Balance of and Change35

Equity (Balance of and Changes in Each Component of AOCI) (Footnote) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 20,662	$ 7,690	$ 2,619	$ (2,496)

Equity (Schedule of Reclassific

Equity (Schedule of Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Investment related gains (losses), net	$ (470)	$ 77,712
Investment income	516,329	514,364
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	137,925	207,844
Income Tax Expense (Benefit)	(37,695)	(62,332)
Net income	100,230	145,512
Unrealized Appreciation Depreciation Of Investments [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Investment related gains (losses), net	(14,456)	(11,857)
Deferred policy acquisition costs attributed to unrealized gains and losses	(6,592)	5,848
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(21,274)	(5,762)
Income Tax Expense (Benefit)	4,678	3,194
Net income	(16,596)	(2,568)
Amortization Of Unrealized Pension And Postretirement Benefits [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Prior service cost	246	82
Actuarial gains/(losses)	(1,592)	(1,538)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(1,346)	(1,456)
Income Tax Expense (Benefit)	283	510
Net income	(1,063)	(946)
Amounts Reclassified From AOCI [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net income	(17,659)	(3,514)
Interest Rate Options [Member] | Unrealized Appreciation Depreciation Of Investments [Member] | Unrealized Gains Losses On Available For Sale Securities [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(370)	0
Currency Swap [Member] | Unrealized Appreciation Depreciation Of Investments [Member] | Unrealized Gains Losses On Available For Sale Securities [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	144	197
Forward Contracts [Member] | Unrealized Appreciation Depreciation Of Investments [Member] | Unrealized Gains Losses On Available For Sale Securities [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 0	$ 50

Equity (Narrative) (Details)

Equity (Narrative) (Details) $ in Millions	Mar. 31, 2018USD ($)
Equity [Abstract]
Stock Repurchase Program, Authorized Amount	$ 400

Equity Based Compensation (Narr

Equity Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity compensation expense	$ 9.7	$ 9.6
Stock appreciation rights granted	200,000
Stock appreciation rights granted, weighted average exercise price (per share)	$ 150.87
Performance contingent units	100,000
Shares Granted To Non Employee Directors	7,263
Options exercisable (shares)	1,700,000
Options exercisable, weighted average price (per share)	$ 68.51
Options, remaining term	4 years 11 months

Investments (Investments in Fix

Investments (Investments in Fixed Maturity and Equity Securities Available-for-Sale by Sector) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 22,890,985	$ 21,966,803
Estimated Fair Value	$ 23,520,469	$ 23,210,968
% of Total	100.00%	100.00%
Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 35,913,705	$ 35,281,412
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2,413,020	2,982,754
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	381,465	113,346
Estimated Fair Value	$ 37,945,260	$ 38,150,820
% of Total	100.00%	100.00%
Other-than-temporary impairments in AOCI	$ 275	$ 275
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		102,841
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		958
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		3,647
Estimated Fair Value		$ 100,152
% of Total		100.00%
Corporate Debt Securities [Member] | Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	22,890,985	$ 21,966,803
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	869,867	1,299,594
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	240,383	55,429
Estimated Fair Value	$ 23,520,469	$ 23,210,968
% of Total	61.90%	60.90%
Other-than-temporary impairments in AOCI	$ 0	$ 0
Canadian and Canadian provincial governments | Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,803,077	2,843,273
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,297,817	1,378,510
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	3,040	1,707
Estimated Fair Value	$ 4,097,854	$ 4,220,076
% of Total	10.80%	11.10%
Other-than-temporary impairments in AOCI	$ 0	$ 0
Residential mortgage-backed securities | Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,791,007	1,695,126
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	23,640	36,632
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	27,499	11,878
Estimated Fair Value	$ 1,787,148	$ 1,719,880
% of Total	4.70%	4.50%
Other-than-temporary impairments in AOCI	$ 0	$ 0
Asset-backed securities | Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,727,810	1,634,758
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	16,383	18,798
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	9,471	5,194
Estimated Fair Value	$ 1,734,722	$ 1,648,362
% of Total	4.60%	4.30%
Other-than-temporary impairments in AOCI	$ 275	$ 275
Commercial Mortgage Backed Securities [Member] | Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,281,452	1,285,594
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	12,717	22,627
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	12,236	4,834
Estimated Fair Value	$ 1,281,933	$ 1,303,387
% of Total	3.40%	3.40%
Other-than-temporary impairments in AOCI	$ 0	$ 0
US Treasury and Government [Member] | Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,486,262	1,953,436
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	9,266	12,089
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	59,414	21,933
Estimated Fair Value	$ 1,436,114	$ 1,943,592
% of Total	3.80%	5.10%
Other-than-temporary impairments in AOCI	$ 0	$ 0
US States and Political Subdivisions Debt Securities [Member] | Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	672,064	647,727
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	49,465	59,997
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	8,016	4,296
Estimated Fair Value	$ 713,513	$ 703,428
% of Total	1.90%	1.80%
Other-than-temporary impairments in AOCI	$ 0	$ 0
Foreign Government Debt Securities [Member] | Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,261,048	3,254,695
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	133,865	154,507
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	21,406	8,075
Estimated Fair Value	$ 3,373,507	$ 3,401,127
% of Total	8.90%	8.90%
Other-than-temporary impairments in AOCI	$ 0	$ 0
Nonredeemable Preferred Stock [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		41,553
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		479
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		2,226
Estimated Fair Value		$ 39,806
% of Total		39.70%
Equity Securities Other Than Non-redeemable Preferred Stock [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		$ 61,288
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		479
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		1,421
Estimated Fair Value		$ 60,346
% of Total		60.30%

Investments (Fixed Maturity Sec

Investments (Fixed Maturity Securities Pledged And Received As Collateral) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 22,890,985	$ 21,966,803
Available-for-sale Securities	23,520,469	23,210,968
Collateral Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	72,850	72,542
Available-for-sale Securities	75,384	75,622
Collateral Received Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	614,423	590,417
Reported Value Measurement [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held-in-trust	16,316,662	15,584,296
Estimate of Fair Value Measurement [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held-in-trust	$ 17,076,547	$ 16,715,281

Investments (Exposure To Concen

Investments (Exposure To Concentrations Of Credit Risk) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 22,890,985	$ 21,966,803
Available-for-sale Securities	23,520,469	23,210,968
Canadian Province Of Quebec Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,106,753	939,837
Available-for-sale Securities	1,863,568	1,282,944
Canadian Province Of Ontario Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	928,384	1,119,337
Available-for-sale Securities	$ 1,247,158	$ 1,917,996

Investments (Amortized Cost and

Investments (Amortized Cost and Fair Value of Fixed Maturities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Available For Sale Securities Debt Maturities Amortized Cost
Due in one year or less	$ 900,166
Due after one year through five years	7,939,821
Due after five year through ten years	9,533,025
Due after ten years	12,740,424
Asset and mortgage-backed securities	4,800,269
Total	35,913,705	$ 35,281,412
Available For Sale Securities Debt Maturities Fair Value
Due in one year or less	905,385
Due after one year through five years	8,084,053
Due after five year through ten years	9,779,934
Due after ten years	14,372,085
Asset and mortgage-backed securities	4,803,803
Total	$ 37,945,260	$ 38,150,820

Investments (Amortized Cost a43

Investments (Amortized Cost and Fair Value of Fixed Maturity Holdings by Industry Type) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Corporate Securities by Investment Sector And Credit Rating [Line Items]
Amortized Cost	$ 22,890,985	$ 21,966,803
Estimated Fair Value	$ 23,520,469	$ 23,210,968
% of Total	100.00%	100.00%
Finance
Corporate Securities by Investment Sector And Credit Rating [Line Items]
Amortized Cost	$ 8,250,681	$ 7,977,885
Estimated Fair Value	$ 8,407,037	$ 8,362,774
% of Total	35.80%	36.10%
Industrial
Corporate Securities by Investment Sector And Credit Rating [Line Items]
Amortized Cost	$ 12,093,034	$ 11,535,166
Estimated Fair Value	$ 12,437,180	$ 12,199,333
% of Total	52.80%	52.50%
Utility
Corporate Securities by Investment Sector And Credit Rating [Line Items]
Amortized Cost	$ 2,547,270	$ 2,453,752
Estimated Fair Value	$ 2,676,252	$ 2,648,861
% of Total	11.40%	11.40%

Investments (Credit Losses Reco

Investments (Credit Losses Recognized in Earnings on Fixed Maturity Securities Held by the Company) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Investments [Abstract]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	$ 3,677	$ 3,677	$ 3,677	$ 6,013
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Change in Status	$ 0	$ (2,336)

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	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 381,465	$ 116,993
% of Total	100.00%	100.00%
Less than 20%
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 358,873	$ 113,466
% of Total	94.10%	97.00%
20% or more for less than six months
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 20,232	$ 689
% of Total	5.30%	0.60%
20% or more for six months or greater
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 2,360	$ 2,838
% of Total	0.60%	2.40%

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	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months		$ 4,565,273
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss		40,239
Estimated Fair Value - 12 months or greater		2,738,393
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss		73,107
Estimated Fair Value		7,303,666
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss		113,346
Equity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months		5,902
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss		1,024
Estimated Fair Value - 12 months or greater		73,722
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss		2,623
Estimated Fair Value		79,624
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss		3,647
Non-investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months		225,474
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss		3,450
Estimated Fair Value - 12 months or greater		93,723
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss		7,559
Estimated Fair Value		319,197
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss		11,009
Investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	$ 10,738,781	4,339,799
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	226,619	36,789
Estimated Fair Value - 12 months or greater	2,440,830	2,644,670
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	115,895	65,548
Estimated Fair Value	13,179,611	6,984,469
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	342,514	102,337
Corporate Debt Securities [Member] | Non-investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	452,086	194,879
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	29,597	3,317
Estimated Fair Value - 12 months or greater	46,976	75,731
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	8,337	6,933
Estimated Fair Value	499,062	270,610
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	37,934	10,250
Corporate Debt Securities [Member] | Investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	7,282,079	1,886,212
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	155,541	17,099
Estimated Fair Value - 12 months or greater	883,699	1,009,750
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	46,908	28,080
Estimated Fair Value	8,165,778	2,895,962
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	202,449	45,179
Canadian and Canadian provincial governments | Non-investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	1,900	1,995
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	114	20
Estimated Fair Value - 12 months or greater	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	0	0
Estimated Fair Value	1,900	1,995
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	114	20
Canadian and Canadian provincial governments | Investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	39,192	18,688
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	390	91
Estimated Fair Value - 12 months or greater	109,552	111,560
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	2,536	1,596
Estimated Fair Value	148,744	130,248
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	2,926	1,687
Residential mortgage-backed securities | Non-investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	0	0
Estimated Fair Value - 12 months or greater	1,272	1,369
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	25	22
Estimated Fair Value	1,272	1,369
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	25	22
Residential mortgage-backed securities | Investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	897,255	566,699
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	19,899	5,852
Estimated Fair Value - 12 months or greater	225,288	224,439
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	7,575	6,004
Estimated Fair Value	1,122,543	791,138
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	27,474	11,856
Asset-backed securities | Non-investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	0	0
Estimated Fair Value - 12 months or greater	1,173	1,489
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	47	53
Estimated Fair Value	1,173	1,489
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	47	53
Asset-backed securities | Investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	612,053	434,274
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	7,001	2,707
Estimated Fair Value - 12 months or greater	114,605	168,524
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	2,423	2,434
Estimated Fair Value	726,658	602,798
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	9,424	5,141
Commercial mortgage-backed securities | Non-investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	57,385
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	662
Estimated Fair Value - 12 months or greater	12,045
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	169
Estimated Fair Value	69,430
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	831
Commercial mortgage-backed securities | Investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	538,464	220,401
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	8,026	1,914
Estimated Fair Value - 12 months or greater	103,447	103,269
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	4,210	2,920
Estimated Fair Value	641,911	323,670
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	12,236	4,834
US Government Agencies Debt Securities [Member] | Investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	488,095	800,298
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	16,856	6,177
Estimated Fair Value - 12 months or greater	744,844	767,197
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	42,558	15,756
Estimated Fair Value	1,232,939	1,567,495
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	59,414	21,933
US States and Political Subdivisions Debt Securities [Member] | Non-investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	511,371
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	30,373
Estimated Fair Value - 12 months or greater	61,466
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	8,578
Estimated Fair Value	572,837
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	38,951
US States and Political Subdivisions Debt Securities [Member] | Investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	135,158	43,510
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	3,331	242
Estimated Fair Value - 12 months or greater	67,949	68,666
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	4,685	4,054
Estimated Fair Value	203,107	112,176
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	8,016	4,296
Foreign Government Debt Securities [Member] | Non-investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	11,250,152	28,600
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	256,992	113
Estimated Fair Value - 12 months or greater	2,502,296	15,134
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	124,473	551
Estimated Fair Value	13,752,448	43,734
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	381,465	664
Foreign Government Debt Securities [Member] | Investment grade securities | Fixed maturity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months	746,485	369,717
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	15,575	2,707
Estimated Fair Value - 12 months or greater	191,446	191,265
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	5,000	4,704
Estimated Fair Value	937,931	560,982
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	$ 20,575	7,411
Nonredeemable Preferred Stock [Member] | Equity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months		82
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss		1
Estimated Fair Value - 12 months or greater		26,471
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss		2,225
Estimated Fair Value		26,553
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss		2,226
Other equity securities | Equity securities
Estimated Fair Values And Gross Unrealized Losses, OTTI Impairment Losses Reported In AOCI [Line Items]
Estimated Fair Value - Less than 12 months		5,820
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss		1,023
Estimated Fair Value - 12 months or greater		47,251
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss		398
Estimated Fair Value		53,071
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss		$ 1,421

Investments (Investment Income

Investments (Investment Income Net of Related Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 538,382	$ 533,034
Investment expense	(22,053)	(18,670)
Investment income, net of related expenses	516,329	514,364
Available-for-sale Securities [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	369,203	324,500
Equity Securities [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	1,682	1,359
Mortgage Loans on Real Estate [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	50,199	44,347
Policy loans
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	14,780	15,272
Funds withheld at interest
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	75,445	127,578
Short-term Investments [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	3,245	1,510
Other invested assets
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 23,828	$ 18,468

Investments (Investment Related

Investments (Investment Related Gains (Losses) Net) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Investments [Abstract]
Available-for-sale Securities, Realized Losses, Excluding Other than Temporary Impairments	$ (20,380)	$ (8,687)
Available-for-sale Equity Securities, Gross Unrealized Gain	28	0
Available-for-sale Equity Securities, Gross Unrealized Loss	(950)	(3,876)
Gain (Loss) on Sale of Equity Investments	(4,137)	0
Investment Gains And Losses [Abstract]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net	0	17,189
Gain on investment activity	10,966	17,893
Other impairment losses and change in mortgage loan provision	(312)	(99)
Derivatives and other, net	14,315	72,481
Total investment related gains (losses), net	$ (470)	$ 60,523

Investments (Borrowed Securitie

Investments (Borrowed Securities Repurchased Securities And Repurchased Reversed Repurchased Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Securities Loaned, Fair Value of Collateral	$ 118,617	$ 121,551
Securities Received as Collateral	128,000	128,000
Securities for Reverse Repurchase Agreements	403,135	413,819
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities	404,871	417,550
Reported Value Measurement [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Borrowed	353,875	358,875
Securities Loaned, Fair Value of Collateral	117,449	117,246
Estimate of Fair Value Measurement [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Borrowed	370,760	377,820
Securities for Reverse Repurchase Agreements	$ 411,988	$ 428,344

Investments (Securities Pledged

Investments (Securities Pledged as Collateral Related to Repurchase Reverse Repurchase Program) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Fair Value of Collateral	$ 118,617	$ 121,551
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	411,988	428,344
Obligation to Return Securities Received as Collateral	530,605	549,895
Securities Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	563,587	576,786
SecuredBorrowingsGrossDifferenceAmount	32,982	26,891
Corporate Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Fair Value of Collateral	118,617	121,551
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	171,678	184,646
Residential Mortgage Backed Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
US Treasury and Government [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	219,509	220,765
Foreign Government Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	19,670	21,802
Other Debt Obligations [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	1,131	1,131
Maturity Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	1,131	1,131
Obligation to Return Securities Received as Collateral	1,131	1,131
Maturity Overnight [Member] | Corporate Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Fair Value of Collateral	0	0
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity Overnight [Member] | Residential Mortgage Backed Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity Overnight [Member] | US Treasury and Government [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity Overnight [Member] | Foreign Government Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity Overnight [Member] | Other Debt Obligations [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	1,131	1,131
Maturity up to 30 days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Obligation to Return Securities Received as Collateral	0	0
Maturity up to 30 days [Member] | Corporate Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Fair Value of Collateral	0	0
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity up to 30 days [Member] | Residential Mortgage Backed Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity up to 30 days [Member] | US Treasury and Government [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity up to 30 days [Member] | Foreign Government Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity up to 30 days [Member] | Other Debt Obligations [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	312
Obligation to Return Securities Received as Collateral	0	312
Maturity 30 to 90 Days [Member] | Corporate Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Fair Value of Collateral	0	0
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	312
Maturity 30 to 90 Days [Member] | Residential Mortgage Backed Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity 30 to 90 Days [Member] | US Treasury and Government [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity 30 to 90 Days [Member] | Foreign Government Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity 30 to 90 Days [Member] | Other Debt Obligations [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity over 90 days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	410,857	426,901
Obligation to Return Securities Received as Collateral	529,474	548,452
Maturity over 90 days [Member] | Corporate Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned, Fair Value of Collateral	118,617	121,551
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	171,678	184,334
Maturity over 90 days [Member] | Residential Mortgage Backed Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	0	0
Maturity over 90 days [Member] | US Treasury and Government [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	219,509	220,765
Maturity over 90 days [Member] | Foreign Government Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	19,670	21,802
Maturity over 90 days [Member] | Other Debt Obligations [Member]
Assets Sold under Agreements to Repurchase [Line Items]
FinancialAssetsSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	$ 0	$ 0

Investments (Mortgage Loans by

Investments (Mortgage Loans by Property Type) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Mortgage Loans on Real Estate [Line Items]
Percentage of total	100.00%	100.00%
Recorded investment	$ 4,450,291	$ 4,413,171
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	(3,433)	(3,254)
Allowance for Loan and Lease Losses, Real Estate	(8,864)	(9,384)	$ (7,786)	$ (7,685)
Mortgage loans on real estate (net of allowances of $8,864 and $9,384)	$ 4,437,994	$ 4,400,533
Apartment
Mortgage Loans on Real Estate [Line Items]
Percentage of total	11.20%	11.60%
Recorded investment	$ 497,699	$ 510,052
Retail
Mortgage Loans on Real Estate [Line Items]
Percentage of total	27.80%	28.80%
Recorded investment	$ 1,236,933	$ 1,270,676
Office building
Mortgage Loans on Real Estate [Line Items]
Percentage of total	34.10%	33.60%
Recorded investment	$ 1,518,170	$ 1,487,392
Industrial
Mortgage Loans on Real Estate [Line Items]
Percentage of total	21.70%	21.30%
Recorded investment	$ 964,685	$ 938,612
Other commercial
Mortgage Loans on Real Estate [Line Items]
Percentage of total	5.20%	4.70%
Recorded investment	$ 232,804	$ 206,439

Investments (Mortgage Loans b52

Investments (Mortgage Loans by Maturity Date) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 4,450,291	$ 4,413,171
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%	100.00%
Due within five years
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 1,130,108	$ 1,091,066
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	25.40%	24.80%
Due after five years through ten years
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 2,492,588	$ 2,516,872
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	56.00%	57.00%
Due after ten years
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 827,595	$ 805,233
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	18.60%	18.20%

Investments (Mortgage Loans b53

Investments (Mortgage Loans by Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 4,450,291	$ 4,413,171
Loans Receivable, Gross, Commercial, Construction	$ 12,279	$ 9,686
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%	100.00%
Mortgage Loans By Credit Quality Indicator Range Four [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 160,433	$ 167,611
Loans Receivable, Gross, Commercial, Construction	$ 0	$ 9,686
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	3.60%	3.80%
Mortgage Loans By Credit Quality Indicator Range Three [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 418,769	$ 431,274
Loans Receivable, Gross, Commercial, Construction	$ 0	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	9.40%	9.80%
Mortgage Loans By Credit Quality Indicator Range Two [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 1,617,873	$ 1,608,078
Loans Receivable, Gross, Commercial, Construction	$ 0	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	36.40%	36.40%
Mortgage Loans By Credit Quality Indicator Range One [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 2,253,216	$ 2,206,208
Loans Receivable, Gross, Commercial, Construction	$ 12,279	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	50.60%	50.00%
Debt Service Coverage Ratio Range Three [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 110,105	$ 69,451
Debt Service Coverage Ratio Range Three [Member] | Mortgage Loans By Credit Quality Indicator Range Four [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	4,276	6,362
Debt Service Coverage Ratio Range Three [Member] | Mortgage Loans By Credit Quality Indicator Range Three [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	30,904	15,367
Debt Service Coverage Ratio Range Three [Member] | Mortgage Loans By Credit Quality Indicator Range Two [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	68,070	43,921
Debt Service Coverage Ratio Range Three [Member] | Mortgage Loans By Credit Quality Indicator Range One [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	6,855	3,801
Debt Service Coverage Ratio Range Two [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	167,712	151,281
Debt Service Coverage Ratio Range Two [Member] | Mortgage Loans By Credit Quality Indicator Range Four [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	30,497	30,713
Debt Service Coverage Ratio Range Two [Member] | Mortgage Loans By Credit Quality Indicator Range Three [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	27,682	19,461
Debt Service Coverage Ratio Range Two [Member] | Mortgage Loans By Credit Quality Indicator Range Two [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	29,795	47,128
Debt Service Coverage Ratio Range Two [Member] | Mortgage Loans By Credit Quality Indicator Range One [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	79,738	53,979
Debt Service Coverage Ratio Range One [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	4,160,195	4,182,753
Debt Service Coverage Ratio Range One [Member] | Mortgage Loans By Credit Quality Indicator Range Four [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	125,660	120,850
Debt Service Coverage Ratio Range One [Member] | Mortgage Loans By Credit Quality Indicator Range Three [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	360,183	396,446
Debt Service Coverage Ratio Range One [Member] | Mortgage Loans By Credit Quality Indicator Range Two [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	1,520,008	1,517,029
Debt Service Coverage Ratio Range One [Member] | Mortgage Loans By Credit Quality Indicator Range One [Member]
Mortgage Loans on Real Estate [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 2,154,344	$ 2,148,428

Investments (Mortgage Loans Age

Investments (Mortgage Loans Age Analysis) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 19,158	$ 19,156
Financing Receivable, Recorded Investment, Current	4,431,133	4,394,015
Loans Receivable, Gross, Commercial, Real Estate	4,450,291	4,413,171
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	17,102	17,100
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	2,056
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 2,056	$ 0

Investments (Mortgage Loans b55

Investments (Mortgage Loans by Method of Evaluation and Related Valuation Allowances) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Mortgage Loans:
Recorded investment	$ 4,450,291	$ 4,413,171
Valuation Allowances:
Allowance for Loan and Lease Losses, Real Estate	8,864	9,384	$ 7,786	$ 7,685
Commercial Real Estate Portfolio Segment [Member]
Mortgage Loans:
Evaluated individually for credit losses	23,423	5,858
Evaluated collectively for credit losses	4,426,868	4,407,313
Recorded investment	4,450,291	4,413,171
Valuation Allowances:
Specific for credit losses	0	0
Non-specifically identified credit losses	8,864	9,384
Allowance for Loan and Lease Losses, Real Estate	$ 8,864	$ 9,384

Investments (Loan Valuation All

Investments (Loan Valuation Allowance for Mortgage Loans) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Allowance For Loan And Lease Losses Roll Forward
Balance, Beginning of Period	$ 9,384	$ 7,685
Provision (release)	(516)	101
Valuation Allowances and Reserves, Additions for Adjustments	(4)	0
Balance, End of Period	$ 8,864	$ 7,786

Investments (Impaired Mortgage

Investments (Impaired Mortgage Loans) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Financing Receivable Impaired [Line Items]
Unpaid Principal Balance		$ 0		$ 6,427
Recorded Investment		23,423		5,858
Related Allowance		0		0
Carrying Value		23,423		5,858
Average Investment	[1]	14,640	$ 2,157
Interest Income		56	33
Impaired mortgage loans with valuation allowance recorded
Financing Receivable Impaired [Line Items]
Unpaid Principal Balance		0		0
Recorded Investment		0		0
Related Allowance		0		0
Carrying Value		0		0
Average Investment	[1]	0	0
Interest Income		0	0
Impaired mortgage loans with no valuation allowance recorded
Financing Receivable Impaired [Line Items]
Unpaid Principal Balance		0		6,427
Recorded Investment		23,423		5,858
Related Allowance		0		0
Carrying Value		23,423		$ 5,858
Average Investment	[1]	14,640	2,157
Interest Income		$ 56	$ 33
[1]	verage 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	Mar. 31, 2018	Dec. 31, 2017
Other invested assets	$ 1,512,147	$ 1,505,332
Limited Partner [Member]
Other invested assets	805,613	781,124
Equity Release Mortgages [Member]
Other invested assets	261,837	219,940
Derivatives
Other invested assets	132,195	137,613
Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Other invested assets	221,512	218,541
Other
Other invested assets	$ 90,990	$ 148,114

Investments (Narrative) (Detail

Investments (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)securities	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)securities	Dec. 31, 2016USD ($)
Investment Narrative [Line Items]
Proceeds From Sale Of Available For Sale Securities Sold At Loss	$ 1,263,600	$ 428,600
Sales of fixed maturity securities available-for-sale	1,898,722	1,563,956
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Cash	30,700		$ 31,200
Derivative Instruments, Gain Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing	2,400	1,000
Net Amount Assets Liabilities From Repurchase Reverse Repurchase Agreements	400		1,100
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	$ 3,677	3,677	$ 3,677	$ 6,013
Policy Loans Percent Of Total Investments	2.60%		2.60%
Mortgage Loan Percent Of Cash And Invested Assets	8.60%		8.50%
Available-for-sale Securities, Realized Losses, Excluding Other than Temporary Impairments	$ 20,380	8,687
Proceeds From Sale Of Available For Sale Equity Securities Sold At Loss	28,400	147,600
Available-for-sale Equity Securities, Gross Unrealized Loss	950	3,876
Available-for-sale Securities, Gross Realized Gains	$ 10,966	17,893
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities	2,114		1,116
Securities As Percentage Of Consolidated Stockholder Equity	10.00%
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%		100.00%
Funds Withheld At Interest Percent Of Total Investments	11.70%		11.80%
Funds withheld at interest	$ 6,005,892		$ 6,083,388
Funds Held Under Reinsurance Agreements Asset Specific Client	$ 4,000,000
Other Invested Assets Percent Of Cash And Invested Assets	2.90%		2.90%
Gain (Loss) on Sale of Equity Investments	$ (4,137)	$ 0
CALIFORNIA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	19.60%
TEXAS
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	8.60%
GEORGIA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	7.50%
CANADA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	2.40%

Derivative Instruments (Gross N

Derivative Instruments (Gross Notional Amount and Fair Value of Derivatives Contracts) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Notional Amount	$ 16,791,770	$ 15,904,127
Carrying Value / Fair Value of Assets	331,273	320,724
Derivative Liability, Fair Value, Gross Liability	990,777	1,058,727
Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	15,059,954	14,243,031
Carrying Value / Fair Value of Assets	268,531	254,252
Derivative Liability, Fair Value, Gross Liability	968,119	1,022,122
Not Designated as Hedging Instrument | Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount	1,021,739	996,204
Carrying Value / Fair Value of Assets	47,303	59,809
Derivative Liability, Fair Value, Gross Liability	152	2,372
Not Designated as Hedging Instrument | Financial Futures
Derivative [Line Items]
Notional Amount	388,874	412,438
Carrying Value / Fair Value of Assets	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Not Designated as Hedging Instrument | Foreign Currency Forwards
Derivative [Line Items]
Notional Amount	6,012	6,030
Carrying Value / Fair Value of Assets	48	0
Derivative Liability, Fair Value, Gross Liability	4	28
Not Designated as Hedging Instrument | Consumer Price Index Swap [Member]
Derivative [Line Items]
Notional Amount	218,237	221,932
Carrying Value / Fair Value of Assets	127	0
Derivative Liability, Fair Value, Gross Liability	427	2,160
Not Designated as Hedging Instrument | Credit Default Swaps
Derivative [Line Items]
Notional Amount	933,200	961,200
Carrying Value / Fair Value of Assets	7,279	8,319
Derivative Liability, Fair Value, Gross Liability	1,058	1,651
Not Designated as Hedging Instrument | Equity Options
Derivative [Line Items]
Notional Amount	639,801	632,251
Carrying Value / Fair Value of Assets	33,958	23,271
Derivative Liability, Fair Value, Gross Liability	0	0
Not Designated as Hedging Instrument | Longevity Swap [Member]
Derivative [Line Items]
Notional Amount	985,920	960,400
Carrying Value / Fair Value of Assets	44,011	40,659
Derivative Liability, Fair Value, Gross Liability	0	0
Not Designated as Hedging Instrument | Mortality Swap [Member]
Derivative [Line Items]
Notional Amount	0	0
Carrying Value / Fair Value of Assets	0	0
Derivative Liability, Fair Value, Gross Liability	1,683	1,683
Not Designated as Hedging Instrument | Synthetic Guaranteed Investment Contracts
Derivative [Line Items]
Notional Amount	10,866,171	10,052,576
Carrying Value / Fair Value of Assets	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Not Designated as Hedging Instrument | Embedded Derivatives In Modified Coinsurance Or Funds Withheld Arrangements
Derivative [Line Items]
Notional Amount	0	0
Carrying Value / Fair Value of Assets	135,805	122,194
Derivative Liability, Fair Value, Gross Liability	0	0
Not Designated as Hedging Instrument | Embedded Derivatives In Indexed Annuity [Member]
Derivative [Line Items]
Notional Amount	0	0
Carrying Value / Fair Value of Assets	0	0
Derivative Liability, Fair Value, Gross Liability	827,109	861,758
Not Designated as Hedging Instrument | Embedded Derivatives In Variable Annuity [Member]
Derivative [Line Items]
Notional Amount	0	0
Carrying Value / Fair Value of Assets	0	0
Derivative Liability, Fair Value, Gross Liability	137,686	152,470
Designated As Hedging Instrument
Derivative [Line Items]
Notional Amount	1,731,816	1,661,096
Carrying Value / Fair Value of Assets	62,742	66,472
Derivative Liability, Fair Value, Gross Liability	22,658	36,605
Designated As Hedging Instrument | Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount	435,000	435,000
Carrying Value / Fair Value of Assets	(1,119)	0
Derivative Liability, Fair Value, Gross Liability	16,972	20,389
Designated As Hedging Instrument | Currency Swap [Member]
Derivative [Line Items]
Notional Amount	598,575	672,921
Carrying Value / Fair Value of Assets	56,403	65,207
Derivative Liability, Fair Value, Gross Liability	5,461	8,496
Designated As Hedging Instrument | Forward Contracts [Member]
Derivative [Line Items]
Notional Amount	698,241	553,175
Carrying Value / Fair Value of Assets	7,458	1,265
Derivative Liability, Fair Value, Gross Liability	$ 225	$ 7,720

Derivative Instruments (Derivat

Derivative Instruments (Derivative Instruments Offsetting Balance Sheet) (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Derivative Assets [Abstract]
Derivative Fair Value Of Free Standing Derivative Asset		$ 195,468	$ 198,530
Gross Amounts Offset in the Balance Sheet		(19,262)	(20,258)
Net Amounts Presented in the Balance Sheet		176,206	178,272
Derivative Asset, Fair Value of Collateral	[1]	0	(862)
Gross Amounts Not Offset in the Balance Sheet - Cash Collateral Pledged/Received	[2]	(188,407)	(185,900)
Net Amount		(12,201)	(8,490)
Derivative Liabilities [Abstract]
Derivative Fair Value Of Free Standing Derivative Liability		25,982	44,499
Gross Amounts Offset in the Balance Sheet		(19,262)	(20,258)
Net Amounts Presented in the Balance Sheet		6,720	24,241
Gross Amounts Not Offset in the Balance Sheet - Financial Instruments	[3]	(57,456)	(58,156)
Gross Amounts Not Offset in the Balance Sheet - Cash Collateral Pledged/Received	[4]	(3,470)	(22,221)
Net Amount		$ (54,206)	$ (56,136)
[1]	Consists of U.S. Treasury and government securities.
[2]	Included in cash and cash equivalents, with obligation to return cash collateral recorded in other liabilities.
[3]	Included in available-for-sale securities, primarily consists of U.S. Treasury and government agency securities.
[4]	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	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	$ (1,891)	$ 6,536
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	1,891	(6,536)
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net	$ 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	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ (20,662)	$ (7,690)	$ (2,619)	$ 2,496
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	17,817	10,433
Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(144)	(247)
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 370	$ 0

Derivative Instruments (Cash Fl

Derivative Instruments (Cash Flow Hedges) (Details) - Cash Flow Hedging [Member] - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ 17,817	$ 10,433
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	20,662	7,690	$ 2,619	$ (2,496)
Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	144	247
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(370)	0
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	14,986	2,216
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
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	(370)	0
Currency Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	2,831	8,217
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	144	197
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	0	0
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	0	50
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

Derivative Instruments (Hedges

Derivative Instruments (Hedges of Net Investments in Foreign Operations) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Net Derivatives Gains (Losses) Deferred in AOCI	[1],[2]	$ 8,805	$ (7,606)
Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Net Derivatives Gains (Losses) Deferred in AOCI	[1],[2]	$ 12,236	$ 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	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ (470)	$ 60,523
Policy acquisition costs and other insurance expenses	(356,902)	(379,389)
Interest credited	(80,449)	(107,684)
Other revenues	75,297	68,157
Gain Loss On Investments Related To Change In Fair Value Of Derivatives Excluding Embedded Derivatives	(19,475)	(22,849)
Not Designated as Hedging Instrument
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	34,272	51,814
Not Designated as Hedging Instrument | Interest Rate Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(26,571)	(2,612)
Not Designated as Hedging Instrument | Financial Futures
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	129	(12,775)
Not Designated as Hedging Instrument | Foreign Currency Forwards
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	323	904
Not Designated as Hedging Instrument | Consumer Price Index Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	2,186	(5)
Not Designated as Hedging Instrument | Credit Default Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(402)	7,358
Not Designated as Hedging Instrument | Equity Options
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	2,593	(17,189)
Not Designated as Hedging Instrument | Longevity Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Other revenues	2,267	1,865
Not Designated as Hedging Instrument | Mortality Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Other revenues	0	(395)
Not Designated as Hedging Instrument | Embedded Derivatives In Modified Coinsurance Or Funds Withheld Arrangements
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	13,611	68,702
Not Designated as Hedging Instrument | Embedded Derivatives In Indexed Annuity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Interest credited	(25,351)	16,402
Not Designated as Hedging Instrument | Embedded Derivatives In Variable Annuity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ 14,785	$ 22,363

Derivative Instruments (Exposur

Derivative Instruments (Exposure from Credit Derivatives by Rating of the Underlying Credits) (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Credit Derivatives [Line Items]
Credit Derivative Current Fair Value	[1]	$ 7,095	$ 7,572
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 923,300	$ 951,300
Derivative Average Remaining Maturity	[1],[3]	3 years 2 months	3 years 5 months
Standard Poors AAA To A Minus Ratings [Member] | Single Name Credit Default Swaps [Member]
Credit Derivatives [Line Items]
Credit Derivative Current Fair Value	[1]	$ 2,761	$ 3,128
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 152,000	$ 162,000
Derivative Average Remaining Maturity	[1],[3]	3 years	2 years 11 months
Standard Poors AAA To A Minus Ratings [Member] | Credit Default Subtotal [Member]
Credit Derivatives [Line Items]
Credit Derivative Current Fair Value	[1]	$ 2,761	$ 3,128
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 152,000	$ 162,000
Derivative Average Remaining Maturity	[1],[3]	3 years	2 years 11 months
Standard Poors BBB Rating [Member] | Single Name Credit Default Swaps [Member]
Credit Derivatives [Line Items]
Credit Derivative Current Fair Value	[1]	$ 4,203	$ 4,469
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 333,700	$ 361,700
Derivative Average Remaining Maturity	[1],[3]	2 years 9 months	2 years 11 months
Standard Poors BBB Rating [Member] | Credit Default Swaps Referencing Indices [Member]
Credit Derivatives [Line Items]
Credit Derivative Current Fair Value	[1]	$ 156	$ (55)
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 422,600	$ 422,600
Derivative Average Remaining Maturity	[1],[3]	3 years 8 months	4 years
Standard Poors BBB Rating [Member] | Credit Default Subtotal [Member]
Credit Derivatives [Line Items]
Credit Derivative Current Fair Value	[1]	$ 4,359	$ 4,414
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 756,300	$ 784,300
Derivative Average Remaining Maturity	[1],[3]	3 years 3 months	3 years 6 months
Standard & Poor's, BB Rating [Member]
Credit Derivatives [Line Items]
Derivative Average Remaining Maturity	[1],[2]	1 year 6 months	1 year 6 months
Standard & Poor's, BB Rating [Member] | Single Name Credit Default Swaps [Member]
Credit Derivatives [Line Items]
Credit Derivative Current Fair Value	[1]	$ (25)	$ 30
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	15,000	5,000
Standard & Poor's, BB Rating [Member] | Credit Default Subtotal [Member]
Credit Derivatives [Line Items]
Credit Derivative Current Fair Value	[1]	(25)	30
Maximum Potential Future Exposure on Credit Risk Derivatives	[1],[2]	$ 15,000	$ 5,000
[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	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
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	$ 13,611	$ 68,702
Derivative, Gain (Loss) on Derivative, Net	6,850	25,844
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	25,351	(16,402)
Derivative, Gain (Loss) on Derivative, Net	6,537	(21,396)
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	14,785	22,363
Derivative, Gain (Loss) on Derivative, Net	$ 11,126	$ 28,836

Derivative Instruments (Credit

Derivative Instruments (Credit Exposure of Derivative Contracts) (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Credit Exposure of Derivative Contracts
Estimated fair value of derivatives in net asset (liability) position		$ 171,169	$ 155,714
Derivative, Collateral, Right to Reclaim Cash	[1]	3,470	22,221
Derivative Liability, Fair Value of Collateral	[2]	57,456	58,156
Derivative, Collateral, Obligation to Return Cash	[3]	(188,407)	(185,900)
Derivative Asset, Fair Value of Collateral	[4]	0	(862)
Deposits with Clearing Organizations and Others, Securities	[2]	(57,456)	(58,156)
Net credit exposure		(13,768)	(8,827)
Margin account related to exchange-traded futures	[5]	$ 7,382	$ 6,538
[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 securities.
[5]	Included in other assets.

Derivative Instruments (Narrati

Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Cumulative Foreign Currency Translation Gain Loss Recorded In Accumulated Other Comprehensive Income Loss For Terminated Net Investment In Foreign Operations Hedges	$ 134.7		$ 113.7
Derivative Instruments, Gain Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing	2.4	$ 1
Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	0.6
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	$ 0.7

Fair Value of Assets and Liab71

Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Balances of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	$ 37,945,260	$ 38,150,820
Non Redeemable Preferred Stock Equity Method Investments, Fair Value Disclosure		39,806
Equity Method Investments, Fair Value Disclosure	103,983	60,346
Funds withheld at interest embedded derivatives	135,805	122,194
Cash and cash equivalents	538,761	356,788
Short-term investments	58,499	50,746
Investments, Fair Value Disclosure	353,707	356,154
Other Assets, Fair Value Disclosure	44,011	40,659
Assets, Fair Value Disclosure, Recurring	39,180,026	39,177,513
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	964,795	1,014,228
Liabilities Fair Value Disclosure
Liabilities, Fair Value Disclosure, Recurring	971,515	1,038,469
Interest Rate Swaps
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	40,812	51,359
Liabilities Fair Value Disclosure
Other liabilities	(11,752)	(14,311)
Foreign Currency Forwards
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	6,932	730
Liabilities Fair Value Disclosure
Other liabilities	(345)	(7,213)
Consumer Price Index Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	(99)	(221)
Liabilities Fair Value Disclosure
Other liabilities	(201)	(1,939)
Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	221,512	218,541
Credit Default Swaps
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	5,465	5,908
Liabilities Fair Value Disclosure
Other liabilities	(756)	(760)
Equity Option [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	27,140	16,932
Liabilities Fair Value Disclosure
Other liabilities	(6,818)	(6,339)
Currency Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	51,945	62,905
Liabilities Fair Value Disclosure
Other liabilities	(1,003)	(6,194)
Mortality Swap [Member]
Liabilities Fair Value Disclosure
Other liabilities	(1,683)	(1,683)
Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	23,520,469	23,210,968
Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	4,097,854	4,220,076
Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,787,148	1,719,880
Asset-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,734,722	1,648,362
Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,281,933	1,303,387
US Treasury and Government [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,436,114	1,943,592
US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	713,513	703,428
Foreign Government Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	3,373,507	3,401,127
Fair Value Inputs Level 1 Member
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,313,806	1,818,006
Non Redeemable Preferred Stock Equity Method Investments, Fair Value Disclosure		39,806
Equity Method Investments, Fair Value Disclosure	67,831	60,346
Funds withheld at interest embedded derivatives	0	0
Cash and cash equivalents	538,761	354,071
Short-term investments	67	0
Investments, Fair Value Disclosure	221,043	217,618
Other Assets, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure, Recurring	2,141,508	2,489,847
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	0	0
Liabilities Fair Value Disclosure
Liabilities, Fair Value Disclosure, Recurring	0	0
Fair Value Inputs Level 1 Member | Interest Rate Swaps
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 1 Member | Foreign Currency Forwards
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 1 Member | Consumer Price Index Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 1 Member | Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	221,043	217,618
Fair Value Inputs Level 1 Member | Credit Default Swaps
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 1 Member | Equity Option [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 1 Member | Currency Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 1 Member | Mortality Swap [Member]
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 1 Member | Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	0
Fair Value Inputs Level 1 Member | Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	0
Fair Value Inputs Level 1 Member | Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	0
Fair Value Inputs Level 1 Member | Asset-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	0
Fair Value Inputs Level 1 Member | Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	0
Fair Value Inputs Level 1 Member | US Treasury and Government [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,313,806	1,818,006
Fair Value Inputs Level 1 Member | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	0
Fair Value Inputs Level 1 Member | Foreign Government Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	0
Fair Value Inputs Level 2 Member
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	34,438,306	34,098,204
Non Redeemable Preferred Stock Equity Method Investments, Fair Value Disclosure		0
Equity Method Investments, Fair Value Disclosure	0	0
Funds withheld at interest embedded derivatives	0	0
Cash and cash equivalents	0	2,717
Short-term investments	55,215	47,650
Investments, Fair Value Disclosure	132,664	138,536
Other Assets, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure, Recurring	34,626,185	34,287,107
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	0	0
Liabilities Fair Value Disclosure
Liabilities, Fair Value Disclosure, Recurring	5,037	22,558
Fair Value Inputs Level 2 Member | Interest Rate Swaps
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	40,812	51,359
Liabilities Fair Value Disclosure
Other liabilities	(11,752)	(14,311)
Fair Value Inputs Level 2 Member | Foreign Currency Forwards
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	6,932	730
Liabilities Fair Value Disclosure
Other liabilities	(345)	(7,213)
Fair Value Inputs Level 2 Member | Consumer Price Index Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	(99)	(221)
Liabilities Fair Value Disclosure
Other liabilities	(201)	(1,939)
Fair Value Inputs Level 2 Member | Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	469	923
Fair Value Inputs Level 2 Member | Credit Default Swaps
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	5,465	5,908
Liabilities Fair Value Disclosure
Other liabilities	(756)	(760)
Fair Value Inputs Level 2 Member | Equity Option [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	27,140	16,932
Liabilities Fair Value Disclosure
Other liabilities	(6,818)	(6,339)
Fair Value Inputs Level 2 Member | Currency Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	51,945	62,905
Liabilities Fair Value Disclosure
Other liabilities	(1,003)	(6,194)
Fair Value Inputs Level 2 Member | Mortality Swap [Member]
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 2 Member | Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	22,221,205	21,873,696
Fair Value Inputs Level 2 Member | Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	3,525,107	3,626,134
Fair Value Inputs Level 2 Member | Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,666,534	1,611,998
Fair Value Inputs Level 2 Member | Asset-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,604,016	1,524,888
Fair Value Inputs Level 2 Member | Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,280,049	1,300,153
Fair Value Inputs Level 2 Member | US Treasury and Government [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	101,255	103,075
Fair Value Inputs Level 2 Member | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	671,637	662,225
Fair Value Inputs Level 2 Member | Foreign Government Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	3,368,503	3,396,035
Fair Value Inputs Level 3 Member
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	2,193,148	2,234,610
Non Redeemable Preferred Stock Equity Method Investments, Fair Value Disclosure		0
Equity Method Investments, Fair Value Disclosure	36,152	0
Funds withheld at interest embedded derivatives	135,805	122,194
Cash and cash equivalents	0	0
Short-term investments	3,217	3,096
Investments, Fair Value Disclosure	0	0
Other Assets, Fair Value Disclosure	44,011	40,659
Assets, Fair Value Disclosure, Recurring	2,412,333	2,400,559
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	964,795	1,014,228
Liabilities Fair Value Disclosure
Liabilities, Fair Value Disclosure, Recurring	966,478	1,015,911
Fair Value Inputs Level 3 Member | Interest Rate Swaps
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 3 Member | Foreign Currency Forwards
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 3 Member | Consumer Price Index Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 3 Member | Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Fair Value Inputs Level 3 Member | Credit Default Swaps
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 3 Member | Equity Option [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 3 Member | Currency Swap [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	0
Liabilities Fair Value Disclosure
Other liabilities	0	0
Fair Value Inputs Level 3 Member | Mortality Swap [Member]
Liabilities Fair Value Disclosure
Other liabilities	(1,683)	(1,683)
Fair Value Inputs Level 3 Member | Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,299,264	1,337,272
Fair Value Inputs Level 3 Member | Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	572,747	593,942
Fair Value Inputs Level 3 Member | Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	120,614	107,882
Fair Value Inputs Level 3 Member | Asset-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	130,706	123,474
Fair Value Inputs Level 3 Member | Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,884	3,234
Fair Value Inputs Level 3 Member | US Treasury and Government [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	21,053	22,511
Fair Value Inputs Level 3 Member | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	41,876	41,203
Fair Value Inputs Level 3 Member | Foreign Government Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	$ 5,004	$ 5,092

Fair Value of Assets and Liab72

Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Fair Value Assets Transfers between Level 1 and Level 2) (Details) - Available-for-sale Securities [Member] - Corporate Debt Securities [Member] $ in Thousands	Mar. 31, 2017USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	$ 38,675

Fair Value of Assets and Liab73

Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Quantitative Information for Level 3 Inputs) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Corporate Debt Securities [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 183,680	$ 173,579
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%
Fair Value Inputs, Earnings before Interest, Taxes, Depreciation, and Amortization Multiple	6.6
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%
Fair Value Inputs, Earnings before Interest, Taxes, Depreciation, and Amortization Multiple	7.5
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%
Fair Value Inputs, Earnings before Interest, Taxes, Depreciation, and Amortization Multiple	5.9
Longevity Swap [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 44,011	$ 40,659
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%
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] | 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%)
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%
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] | 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 States and Political Subdivisions Debt Securities [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 4,452	$ 4,616
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%
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] | 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%
Equity Securities [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 25,987	$ 0
Equity Securities [Member] | Weighted Average [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Earnings before Interest, Taxes, Depreciation, and Amortization Multiple	8
Equity Securities [Member] | Maximum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Earnings before Interest, Taxes, Depreciation, and Amortization Multiple	13.1
Equity Securities [Member] | Minimum [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Earnings before Interest, Taxes, Depreciation, and Amortization Multiple	6.9
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	$ 827,109	$ 861,758
Embedded Derivatives In Indexed Annuity [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, Lapse Rate, Low End	9.00%	9.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	2.00%	2.00%
Fair Value Inputs Withdrawal	3.00%	3.00%
Fair Value Inputs Option Budget Projection	2.00%	2.00%
Embedded Derivatives In Indexed Annuity [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
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 Withdrawal	5.00%	5.00%
Fair Value Inputs Option Budget Projection	4.00%	4.00%
Embedded Derivatives In Indexed Annuity [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
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 Withdrawal	0.00%	0.00%
Fair Value Inputs Option Budget Projection	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	$ 137,686	$ 152,470
Embedded Derivatives In Variable Annuity [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, Lapse Rate, Low End	5.00%	5.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	1.00%	1.00%
Fair Value Inputs Withdrawal	4.00%	3.00%
Embedded Derivatives In Variable Annuity [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
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%
Fair Value Inputs Withdrawal	7.00%	7.00%
Embedded Derivatives In Variable Annuity [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
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 Withdrawal	0.00%	0.00%
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 Inputs, Entity Credit Risk	1.00%	1.00%
Fair Value Assumptions, Expected Volatility Rate	13.00%	8.00%
Embedded Derivatives In Variable Annuity Contracts [Member] | Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk	5.00%	5.00%
Fair Value Assumptions, Expected Volatility Rate	27.00%	27.00%
Embedded Derivatives In Variable Annuity Contracts [Member] | Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk	0.00%	0.00%
Fair Value Assumptions, Expected Volatility Rate	0.00%	0.00%
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	$ 1,683
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%
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] | 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%
Total Return Swap [Member] | Funds Withheld At Interest Embedded Derivatives [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 135,805	$ 122,194
Total Return Swap [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate, Low End	9.00%	9.00%
Long-Duration Contracts, Assumptions by Product and Guarantee, Mortality Rate, Low End	2.00%	2.00%
Fair Value Inputs Withdrawal	3.00%	3.00%
Fair Value Inputs, Entity Credit Risk	1.00%	1.00%
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]
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 Withdrawal	5.00%	5.00%
Fair Value Inputs, Entity Credit Risk	5.00%	5.00%
Fair Value Inputs Credit Rate	4.00%	4.00%
Total Return Swap [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
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 Withdrawal	0.00%	0.00%
Fair Value Inputs, Entity Credit Risk	0.00%	0.00%
Fair Value Inputs Credit Rate	2.00%	2.00%
Total Return Swap [Member] | US Government Agencies Debt Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 21,053	$ 22,511
Corporate Debt Securities [Member] | Available-for-sale Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value, Equity, Level 1 to Level 2 Transfers, Description	0
Fair Value, Equity, Level 2 to Level 1 Transfers, Description	0

Fair Value of Assets and Liab74

Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Changes in Level 3 Assets and Liabilities) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017		Dec. 31, 2017	Dec. 31, 2016
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		$ 3,234
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(47)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]	(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		1,884
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(1,302)
Commercial Mortgage Backed Securities [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0
Fair Value, Assets 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
US Government Agencies Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		22,511
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(340)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	(96)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]	(1,104)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		21,053
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0
US Government Agencies Debt Securities [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(110)
Fair Value, Assets 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		(110)
US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		41,203
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		700
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]	(35)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		41,876
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0
US States and Political Subdivisions Debt Securities [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		8
Fair Value, Assets 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		8
Foreign Government Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		5,092
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(88)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		5,004	$ 12,344
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0
Foreign Government Debt Securities [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0
Fair Value, Assets 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
Foreign Government Debt Securities [Member] | Other Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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
Funds Withheld At Interest Embedded Derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		122,194	(22,529)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[1]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		135,805	46,173
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3			0
Funds Withheld At Interest Embedded Derivatives [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, Assets 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
Funds Withheld At Interest Embedded Derivatives [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		13,611	68,702
Fair Value, Assets 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		13,611	68,702
Funds Withheld At Interest Embedded Derivatives [Member] | Interest Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, Assets 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
Funds Withheld At Interest Embedded Derivatives [Member] | Other Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, Assets 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
Longevity Swap [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		40,659	26,958
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		1,085	347
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	0	0
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	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		44,011	29,170
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3			0
Longevity Swap [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, Assets 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
Longevity Swap [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, Assets 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
Longevity Swap [Member] | Interest Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, Assets 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
Longevity Swap [Member] | Other Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		2,267	1,865
Fair Value, Assets 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		2,267	1,865
Interest Sensitive Contract Liabilities Embedded Derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value		(964,794)	(972,930)		$ (1,014,229)	$ (990,308)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales	[1]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3		0
Fair Value, 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 Other Comprehensive Income (Loss)		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	[1]	(8,508)	(6,393)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	[1]	17,807	17,811
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3			0
Interest Sensitive Contract Liabilities Embedded Derivatives [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, 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
Interest Sensitive Contract Liabilities Embedded Derivatives [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		12,901	20,300
Fair Value, 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		14,785	22,362
Interest Sensitive Contract Liabilities Embedded Derivatives [Member] | Interest Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(7,544)	34,214
Fair Value, 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		(25,351)	16,402
Interest Sensitive Contract Liabilities Embedded Derivatives [Member] | Other Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, 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
Mortality Swap [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value		(1,683)	(2,857)		$ (1,683)	$ (2,462)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3		0
Fair Value, 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 Other Comprehensive Income (Loss)		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	[1]	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	[1]	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3			0
Mortality Swap [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, 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
Mortality Swap [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, 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
Mortality Swap [Member] | Interest Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, 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
Mortality Swap [Member] | Other Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	395
Fair Value, 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	(395)
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[1]	(28)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]	(48)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		38,905
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		36,152
Equity Securities [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0
Equity Securities [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(2,705)
Fair Value, Assets 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		(2,677)
Equity Securities [Member] | Interest Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0
Fair Value, Assets 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
Equity Securities [Member] | Other Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0
Fair Value, Assets 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
Short-term Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		3,096	3,346
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(25)	33
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		(146)	(32)	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0	(135)	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		3,217	3,276
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3			0
Short-term Investments [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, Assets 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
Short-term Investments [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, Assets 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
Short-term Investments [Member] | Interest Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, Assets 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
Short-term Investments [Member] | Other Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	0
Fair Value, Assets 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
Available-for-sale Securities [Member] | Corporate Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		1,337,272	1,272,253
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(32,852)	4,948
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	(100,170)	(45,914)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[1]	(6,180)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]	(75,146)	(71,470)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		7,166	13,934
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		1,299,264	1,263,925
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(30,805)	0
Available-for-sale Securities [Member] | Corporate Debt Securities [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(361)	(423)
Fair Value, Assets 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		(361)	(423)
Available-for-sale Securities [Member] | Corporate Debt Securities [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			(1,293)
Fair Value, Assets 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	(1,231)
Available-for-sale Securities [Member] | Canadian Provincial Governments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		593,942	475,965
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(24,639)	4,525
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	0	0
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]	0	0
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 Value		572,747	483,560
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0	0
Available-for-sale Securities [Member] | Canadian Provincial Governments [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		3,444	3,070
Fair Value, Assets 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		3,444	3,070
Available-for-sale Securities [Member] | Canadian Provincial Governments [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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
Available-for-sale Securities [Member] | Residential mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		107,882	160,291
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(1,110)	650
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	(20,916)	(16,499)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[1]	0	(10,604)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]	(2,963)	(6,784)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0	77
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		120,614	143,430
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(4,019)	(16,819)
Available-for-sale Securities [Member] | Residential mortgage-backed securities | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(92)	(91)
Fair Value, Assets 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		(92)	(245)
Available-for-sale Securities [Member] | Residential mortgage-backed securities | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			(346)
Fair Value, Assets 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	365
Available-for-sale Securities [Member] | Asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		123,474	219,280
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		853	5,767
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	(11,000)	(10,849)
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]	(2,739)	(18,154)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0	35,258
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		130,706	208,436
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(1,990)	(45,582)
Available-for-sale Securities [Member] | Asset-backed securities | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		106	161
Fair Value, Assets 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		106	1,018
Available-for-sale Securities [Member] | Asset-backed securities | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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		$ 2	0
Available-for-sale Securities [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			21,145
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)			(83)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[1]		(3,720)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]		(5,401)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			1,923
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3			(10,132)
Available-for-sale Securities [Member] | Commercial Mortgage Backed Securities [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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
Available-for-sale Securities [Member] | Commercial Mortgage Backed Securities [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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)
Available-for-sale Securities [Member] | US Treasury and Government [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			24,488
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)			52
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]		(104)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[1]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]		(1,053)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			23,474
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3			0
Available-for-sale Securities [Member] | US Treasury and Government [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			(117)
Fair Value, Assets 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			(117)
Available-for-sale Securities [Member] | US Treasury and Government [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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
Available-for-sale Securities [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			41,666
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)			(843)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]		(33)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			33,858
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3			(6,844)
Available-for-sale Securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			(88)
Fair Value, Assets 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			(88)
Available-for-sale Securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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
Available-for-sale Securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Interest Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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
Available-for-sale Securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Other Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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
Available-for-sale Securities [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			12,869
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)			(191)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]		(334)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3			0
Available-for-sale Securities [Member] | Foreign Government Debt Securities [Member] | Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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
Available-for-sale Securities [Member] | Foreign Government Debt Securities [Member] | Gain (Loss) on Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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
Available-for-sale Securities [Member] | Foreign Government Debt Securities [Member] | Interest Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0
Fair Value, Assets 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
[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 Liab75

Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Assets
Mortgage loans on real estate (net of valuation allowances)		$ 4,437,994	$ 4,400,533
Policy loans		1,346,930	1,357,624
Funds withheld at interest		6,005,892	6,083,388
Cash and cash equivalents		1,510,407	1,303,524	$ 1,178,114	$ 1,200,718
Short-term investments		130,430	93,304
Other invested assets		1,512,147	1,505,332
Accrued investment income		408,338	392,721
Liabilities
Interest-sensitive contract liabilities		16,661,602	16,227,642
Long-term debt		2,788,240	2,788,365
Collateral finance and securitization notes		753,393	783,938
Reported Value Measurement [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)		4,437,994	4,400,533
Policy loans		1,346,930	1,357,624
Funds withheld at interest	[1]	5,865,791	5,955,092
Cash and cash equivalents	[2]	971,646	946,736
Short-term investments	[2]	71,931	42,558
Other invested assets	[2]	690,200	651,792
Accrued investment income		408,338	392,721
Liabilities
Interest-sensitive contract liabilities	[1]	13,169,951	12,683,872
Long-term debt		2,788,240
Debt, Long-term and Short-term, Combined Amount			2,788,365
Collateral finance and securitization notes		753,393	783,938
Estimate of Fair Value Measurement [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)		4,411,472	4,477,654
Policy loans		1,346,930	1,357,624
Funds withheld at interest	[1]	6,098,479	6,275,623
Cash and cash equivalents	[2]	971,646	946,736
Short-term investments	[2]	71,931	42,558
Other invested assets	[2]	710,009	679,377
Accrued investment income		408,338	392,721
Liabilities
Interest-sensitive contract liabilities	[1]	13,151,162	12,917,243
Long-term Debt, Fair Value		2,916,200
Debt, Long-term and Short-term, Combined Amount			2,959,912
Collateral finance and securitization notes		692,696	722,145
Estimate of Fair Value Measurement [Member] | Net Asset Value [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)			0
Policy loans			0
Funds withheld at interest	[1]		0
Cash and cash equivalents	[2]		0
Short-term investments	[2]		0
Other invested assets	[2]		335,125
Accrued investment income			0
Liabilities
Interest-sensitive contract liabilities	[1]		0
Debt, Long-term and Short-term, Combined Amount			0
Collateral finance and securitization notes			0
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 1 Member
Assets
Mortgage loans on real estate (net of valuation allowances)		0	0
Policy loans		0	0
Funds withheld at interest	[1]	0	0
Cash and cash equivalents	[2]	971,646	946,736
Short-term investments	[2]	71,931	42,558
Other invested assets	[2]	10,165	28,540
Accrued investment income		0	0
Liabilities
Interest-sensitive contract liabilities	[1]	0	0
Long-term Debt, Fair Value		0
Debt, Long-term and Short-term, Combined Amount			0
Collateral finance and securitization notes		0	0
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 2 Member
Assets
Mortgage loans on real estate (net of valuation allowances)		0	0
Policy loans		1,346,930	1,357,624
Funds withheld at interest	[1]	0	0
Cash and cash equivalents	[2]	0	0
Short-term investments	[2]	0	0
Other invested assets	[2]	68,903	67,778
Accrued investment income		408,338	392,721
Liabilities
Interest-sensitive contract liabilities	[1]	0	0
Long-term Debt, Fair Value		0
Debt, Long-term and Short-term, Combined Amount			0
Collateral finance and securitization notes		0	0
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 3 Member
Assets
Mortgage loans on real estate (net of valuation allowances)		4,411,472	4,477,654
Policy loans		0	0
Funds withheld at interest	[1]	6,098,479	6,275,623
Cash and cash equivalents	[2]	0	0
Short-term investments	[2]	0	0
Other invested assets	[2]	283,205	247,934
Accrued investment income		0	0
Liabilities
Interest-sensitive contract liabilities	[1]	13,151,162	12,917,243
Long-term Debt, Fair Value		2,916,200
Debt, Long-term and Short-term, Combined Amount			2,959,912
Collateral finance and securitization notes		692,696	$ 722,145
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 3 Member | Net Asset Value [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)		0
Policy loans		0
Funds withheld at interest	[1]	0
Cash and cash equivalents	[2]	0
Short-term investments	[2]	0
Other invested assets	[2]	347,736
Accrued investment income		0
Liabilities
Interest-sensitive contract liabilities	[1]	0
Long-term Debt, Fair Value		0
Collateral finance and securitization notes		$ 0
[1]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjM0ZmNkY2I0YzQ1OTQxNDhiN2RkZTcwZmM1M2JhNDhlfFRleHRTZWxlY3Rpb246NUY0Q0UxRDIwRTdGNjQyQzY1MTUzRUJCNjU5NjBEMTYM}
[2]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjM0ZmNkY2I0YzQ1OTQxNDhiN2RkZTcwZmM1M2JhNDhlfFRleHRTZWxlY3Rpb246NzEyRjAxNTg2MkFFMzYwOTJFNzMzRUJCNjU5NjQ5NTYM}

Fair Value of Assets and Liab76

Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Equity Securities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	$ 38,905

Segment Information (Total Reve

Segment Information (Total Revenues of Reportable Segments) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 3,173,707	$ 3,008,740
Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,703,046	1,787,349
CANADA
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	315,096	276,082
EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	481,925	398,075
Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	634,385	525,682
Corporate and Other [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	39,255	21,552
Life Insurance Product Line [Member] | Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,489,694	1,488,503
Life Insurance Product Line [Member] | CANADA
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	302,319	264,275
Life Insurance Product Line [Member] | EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	393,782	318,086
Life Insurance Product Line [Member] | Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	614,539	505,230
Nontraditional Long-Duration Contracts [Member] | Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	213,352	298,846
Nontraditional Long-Duration Contracts [Member] | CANADA
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	12,777	11,807
Nontraditional Long-Duration Contracts [Member] | EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	88,143	79,989
Nontraditional Long-Duration Contracts [Member] | Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 19,846	$ 20,452

Segment Information (Income Los

Segment Information (Income Loss Before Provision for Income Tax of Reportable Segments) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
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, Noncontrolling Interest	$ 137,925	$ 207,844
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, Noncontrolling Interest	70,313	133,546
CANADA
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, Noncontrolling Interest	26,898	22,920
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, Noncontrolling Interest	54,585	45,894
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, Noncontrolling Interest	26,908	47,560
Corporate and Other [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, Noncontrolling Interest	(40,779)	(42,076)
Life Insurance Product Line [Member] | 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, Noncontrolling Interest	2,892	29,960
Life Insurance Product Line [Member] | CANADA
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, Noncontrolling Interest	23,707	19,328
Life Insurance Product Line [Member] | 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, Noncontrolling Interest	15,421	13,976
Life Insurance Product Line [Member] | 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, Noncontrolling Interest	22,887	41,688
Nontraditional Long-Duration Contracts [Member] | 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, Noncontrolling Interest	67,421	103,586
Nontraditional Long-Duration Contracts [Member] | CANADA
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, Noncontrolling Interest	3,191	3,592
Nontraditional Long-Duration Contracts [Member] | 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, Noncontrolling Interest	39,164	31,918
Nontraditional Long-Duration Contracts [Member] | 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, Noncontrolling Interest	$ 4,021	$ 5,872

Segment Information (Total Asse

Segment Information (Total Assets of Reportable Segments) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 60,954,823	$ 60,514,818
Americas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	35,189,036	34,562,629
CANADA
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,361,000	4,287,824
EMEA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	8,664,626	8,374,488
Asia Pacific [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	6,270,056	6,114,027
Corporate and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	6,470,105	7,175,850
Life Insurance Product Line [Member] | Americas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	18,839,888	18,603,423
Life Insurance Product Line [Member] | CANADA
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,234,253	4,161,452
Life Insurance Product Line [Member] | EMEA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,385,127	3,099,495
Life Insurance Product Line [Member] | Asia Pacific [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	5,095,054	4,915,442
Nontraditional Long-Duration Contracts [Member] | Americas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	16,349,148	15,959,206
Nontraditional Long-Duration Contracts [Member] | CANADA
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	126,747	126,372
Nontraditional Long-Duration Contracts [Member] | EMEA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	5,279,499	5,274,993
Nontraditional Long-Duration Contracts [Member] | Asia Pacific [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 1,175,002	$ 1,198,585

Commitments, Contingencies an80

Commitments, Contingencies and Guarantees (Commitments to Fund Investments) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Limited Partner [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	$ 482,149	$ 485,197
Commercial Loan [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	67,837	40,815
Bank Loans [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	96,808	60,472
Equity Release Mortgages [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	$ 132,523	$ 153,937

Commitments, Contingencies an81

Commitments, Contingencies and Guarantees (Maximum Potential Obligation) (Details) $ in Millions	Mar. 31, 2018USD ($)
Commitment Period Two Thousand Twenty Three [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 500
Commitment Period Two Thousand Thirty Three [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	450
Commitment Period Two Thousand Thirty Four [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	2,000
Commitment Period Two Thousand Thirty Five [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	1,314.2
Commitment Period Two Thousand Thirty Six [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	1,932
Commitment Period Two Thousand Thirty Seven [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	6,750
Commitment Period Two Thousand Thirty Eight [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 800

Commitments, Contingencies an82

Commitments, Contingencies and Guarantees (Guarantees Issued) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Insurance Treaty Guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	$ 949,443	$ 1,047,449
Insurance Treaty Guarantee Net Of Assets Held In Trust [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	832,487	926,393
Guarantee Of Borrowed Securities [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	291,325	294,325
Product Financing Arrangement [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	77,858	86,183
Guarantee Of Lease Obligations [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value	$ 1,465	$ 1,662

Income Tax (Provision for Incom

Income Tax (Provision for Income Tax Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ 28,964	$ 72,745
Tax Adjustments, Settlements, and Unusual Provisions	775	0
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	1,432	(6,153)
Income Tax Reconciliation Foreign Income Tax Basis Differential	(5,760)	(3,383)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	7,947	1,182
Effective Income Tax Rate Reconciliation, Tax Contingency, Domestic, Amount	835	611
Income Tax Reconciliation Change In Foreign Enacted Tax Rate	111	(1,237)
Income Tax Reconciliation SubpartF	658	186
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount	(572)	(126)
Effective Income Tax Rate Reconciliation Global Intangible Low Taxed Income	4,409	0
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount	0	229
Effective Income Tax Rate Reconciliation, Equity in Earnings (Losses) of Unconsolidated Subsidiary, Amount	(1,114)	(1,856)	$ 10,500
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	10	134
Income Tax Expense (Benefit)	$ 37,695	$ 62,332
Effective Income Tax Rate Reconciliation, Percent	27.30%	30.00%

Employee Benefit Plans (Defined

Employee Benefit Plans (Defined Benefit Plans Disclosure) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,654	$ 2,580
Interest cost	1,330	1,198
Expected return on plan assets	(1,554)	(1,285)
Amortization of prior service cost	83	74
Amortization of prior actuarial loss	1,094	1,081
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	257
Total	3,607	3,905
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	636	721
Interest cost	530	565
Expected return on plan assets	0	0
Amortization of prior service cost	(329)	(156)
Amortization of prior actuarial loss	498	457
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0
Total	$ 1,335	$ 1,587

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 0
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	10
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	$ 8

Reinsurance (Ceded Reinsurance

Reinsurance (Ceded Reinsurance Receivable Assets) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 810,554	$ 782,027
Reinsurance Recoverables, Percentage of Total	100.00%	100.00%
Other Reinsurers [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 135,342	$ 127,808
Reinsurance Recoverables, Percentage of Total	16.70%	16.20%
AM Best, A+ Rating [Member] | Reinsurer A [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 317,136	$ 301,478
Reinsurance Recoverables, Percentage of Total	39.10%	38.60%
AM Best, A+ Rating [Member] | Reinsurer B [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 203,137	$ 203,898
Reinsurance Recoverables, Percentage of Total	25.10%	26.10%
AM Best, A+ Rating [Member] | Reinsurer E [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 42,538	$ 40,528
Reinsurance Recoverables, Percentage of Total	5.20%	5.20%
AM Best, A++ Rating [Member] | Reinsurer D [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 42,967	$ 40,592
Reinsurance Recoverables, Percentage of Total	5.30%	5.20%
AM Best, A Rating [Member] | Reinsurer C [Member]
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 69,434	$ 67,723
Reinsurance Recoverables, Percentage of Total	8.60%	8.70%

Reinsurance (Narrative) (Detail

Reinsurance (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Ceded Credit Risk [Line Items]
Reinsurance Claims Recoverables	$ 291.1	$ 243.8
Claims Recoverable From Retrocessionaires Past Due	$ 17.6	$ 1.9
AM Best, A- Rating [Member]
Ceded Credit Risk [Line Items]
Ceded Credit Risk, Disclosure	“A- (excellent)”	“A- (excellent)”

New Accounting Standards New Ac

New Accounting Standards New Accounting Standards (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			$ 156,400
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	$ (1,114)	$ (1,856)	10,500
Contractual Obligation			$ 38,200