American National (ANG-PB) 10-Q 6 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	9 Months Ended
	Sep. 30, 2018	Nov. 01, 2018
Document Information [Line Items]
Entity Registrant Name	AMERICAN EQUITY INVESTMENT LIFE HOLDING CO
Entity Central Index Key	1,039,828
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		90,343,123

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fixed maturity securities:
Available for sale, at fair value (amortized cost: 2018 - $45,688,342; 2017 - $43,116,759)	$ 45,822,017	$ 45,372,989
Held for investment, at amortized cost (fair value: 2018 - $71,113; 2017 - $76,460)	77,213	77,041
Mortgage loans on real estate	2,892,155	2,665,531
Derivative instruments	1,290,387	1,568,380
Other investments	536,594	616,764
Total investments	50,618,366	50,300,705
Cash and cash equivalents	1,129,242	1,434,045
Coinsurance deposits	5,017,255	4,858,289
Accrued investment income	481,999	429,008
Deferred policy acquisition costs	3,318,733	2,714,523
Deferred sales inducements	2,384,161	2,001,892
Deferred income taxes	250,734	38,147
Income taxes recoverable	13,712	0
Other assets	234,796	254,127
Total assets	63,448,998	62,030,736
Liabilities:
Policy benefit reserves	57,992,164	56,142,673
Other policy funds and contract claims	271,765	282,884
Notes payable	494,464	494,093
Subordinated debentures	242,875	242,565
Amounts due under repurchase agreements	116,399	0
Income taxes payable	0	34,285
Other liabilities	1,842,035	1,984,079
Total liabilities	60,959,702	59,180,579
Stockholders' equity:
Preferred stock, par value $1 per share, 2,000,000 shares authorized, 2018 and 2017 - no shares issued and outstanding	0	0
Common stock, par value $1 per share, 200,000,000 shares authorized; issued and outstanding: 2018 - 90,277,626 shares (excluding 1,598,190 treasury shares); 2017 - 89,331,087 shares (excluding 2,064,727 treasury shares)	90,278	89,331
Additional paid-in capital	807,310	791,446
Accumulated other comprehensive income	70,288	724,599
Retained earnings	1,521,420	1,244,781
Total stockholders' equity	2,489,296	2,850,157
Total liabilities and stockholders' equity	$ 63,448,998	$ 62,030,736

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fixed maturity securities:
Available for sale, amortized cost	$ 45,688,342	$ 43,116,759
Held for investment, fair value	$ 71,113	$ 76,460
Stockholders' equity:
Preferred stock, par value (dollars per share)	$ 1	$ 1
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (dollars per share)	$ 1	$ 1
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	90,277,626	89,331,087
Common stock, shares outstanding	90,277,626	89,331,087
Common stock, shares held in treasury	1,598,190	2,064,727

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Premiums and other considerations	$ 7,240	$ 8,569	$ 22,050	$ 25,691
Annuity product charges	58,365	51,931	164,094	144,106
Net investment income	549,391	500,202	1,593,457	1,479,288
Change in fair value of derivatives	595,311	362,525	276,433	1,015,878
Net realized gains (losses) on investments, excluding other than temporary impairment (OTTI) losses	(2,196)	1,579	(40,275)	7,790
OTTI losses on investments:
Total OTTI losses	(14,373)	(273)	(16,025)	(273)
Portion of OTTI losses recognized in (from) other comprehensive income	0	(191)	(1,651)	(1,281)
Net OTTI losses recognized in operations	(14,373)	(464)	(17,676)	(1,554)
Loss on extinguishment of debt	0	(18,389)	0	(18,817)
Total revenues	1,193,738	905,953	1,998,083	2,652,382
Benefits and expenses:
Insurance policy benefits and change in future policy benefits	10,721	10,823	32,091	32,684
Interest sensitive and index product benefits	413,089	501,028	1,355,135	1,392,763
Amortization of deferred sales inducements	55,244	14,707	233,779	110,727
Change in fair value of embedded derivatives	383,716	229,702	(585,465)	628,845
Interest expense on notes and loan payable	6,376	7,597	19,122	23,997
Interest expense on subordinated debentures	3,942	3,502	11,450	10,260
Amortization of deferred policy acquisition costs	81,053	23,023	336,741	162,248
Other operating costs and expenses	31,924	28,782	95,704	82,325
Total benefits and expenses	986,065	819,164	1,498,557	2,443,849
Income before income taxes	207,673	86,789	499,526	208,533
Income tax expense	38,345	29,832	95,333	70,691
Net income	$ 169,328	$ 56,957	$ 404,193	$ 137,842
Earnings per common share	$ 1.87	$ 0.64	$ 4.48	$ 1.55
Earnings per common share - assuming dilution	$ 1.85	$ 0.63	$ 4.42	$ 1.53
Weighted average common shares outstanding: earnings per common share	90,485,567	89,068,770	90,278,209	88,872,562
Weighted average common shares outstanding: earnings per common share - assuming dilution	91,650,886	90,420,530	91,355,410	90,171,020

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income		$ 169,328	$ 56,957	$ 404,193	$ 137,842
Other comprehensive income (loss):
Change in net unrealized investment gains/losses (1)	[1]	(138,863)	75,017	(971,451)	487,486
Noncredit component of OTTI losses (1)	[1]	0	110	775	625
Reclassification of unrealized investment gains/losses to net income (1)	[1]	(525)	825	(19,026)	3,466
Other comprehensive income (loss) before income tax		(139,388)	75,952	(989,702)	491,577
Income tax effect related to other comprehensive income (loss)		29,270	(26,583)	207,837	(172,052)
Other comprehensive income (loss)		(110,118)	49,369	(781,865)	319,525
Comprehensive income (loss)		$ 59,210	$ 106,326	$ (377,672)	$ 457,367
[1]	Net of related adjustments to amortization of deferred sales inducements and deferred policy acquisition costs.

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Retained Earnings
Stockholders' equity at beginning of period at Dec. 31, 2016	$ 2,291,595	$ 88,001	$ 770,344	$ 339,966	$ 1,093,284
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	137,842				137,842
Other comprehensive income (loss)	319,525			319,525
Share-based compensation	5,414		5,414
Issuance of common stock under compensation plans	8,291	933	7,358
Stockholders' equity at end of period at Sep. 30, 2017	2,762,667	88,934	783,116	659,491	1,231,126
Stockholders' equity at beginning of period at Dec. 31, 2017	2,850,157	89,331	791,446	724,599	1,244,781
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	404,193				404,193
Other comprehensive income (loss)	(781,865)			(781,865)
Implementation of accounting standard related to the reclassification of certain tax effects				127,554	(127,554)
Share-based compensation	8,444		8,444
Issuance of common stock under compensation plans	8,367	947	7,420
Stockholders' equity at end of period at Sep. 30, 2018	$ 2,489,296	$ 90,278	$ 807,310	$ 70,288	$ 1,521,420

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parentheticals) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Shares of common stock issued under compensation plans	946,539	932,798

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net income	$ 404,193	$ 137,842
Adjustments to reconcile net income to net cash provided by operating activities:
Interest sensitive and index product benefits	1,355,135	1,392,763
Amortization of deferred sales inducements	233,779	110,727
Annuity product charges	(164,094)	(144,106)
Change in fair value of embedded derivatives	(585,465)	628,845
Change in traditional life and accident and health insurance reserves	2,241	170
Policy acquisition costs deferred	(289,131)	(312,355)
Amortization of deferred policy acquisition costs	336,741	162,248
Provision for depreciation and other amortization	2,584	2,793
Amortization of discounts and premiums on investments	15,315	11,079
Realized (gains) losses on investments and net OTTI losses recognized in operations	57,951	(6,236)
Distributions from equity method investments	1,043	1,191
Change in fair value of derivatives	(276,688)	(1,016,714)
Deferred income taxes	(4,750)	(38,998)
Loss on extinguishment of debt	0	18,817
Share-based compensation	8,444	5,414
Change in accrued investment income	(52,991)	(41,409)
Change in income taxes recoverable/payable	(47,997)	407
Change in other assets	(469)	31
Change in other policy funds and contract claims	(16,203)	(19,941)
Change in collateral held for derivatives	(335,548)	446,920
Change in other liabilities	(48,663)	(62,487)
Other	(9,188)	(11,016)
Net cash provided by operating activities	586,239	1,265,985
Sales, maturities, or repayments of investments:
Fixed maturity securities - available for sale	2,797,834	1,333,829
Mortgage loans on real estate	239,135	240,245
Derivative instruments	1,252,754	1,150,793
Other investments	156,536	8,182
Acquisitions of investments:
Fixed maturity securities - available for sale	(5,215,295)	(3,755,011)
Mortgage loans on real estate	(465,473)	(370,229)
Derivative instruments	(642,849)	(494,226)
Other investments	(67,646)	(18,654)
Purchases of property, furniture and equipment	(3,510)	(3,894)
Net cash used in investing activities	(1,948,514)	(1,908,965)
Financing activities
Receipts credited to annuity and single premium universal life policyholder account balances	3,255,014	3,151,516
Coinsurance deposits	(53,806)	30,892
Return of annuity policyholder account balances	(2,248,876)	(2,048,967)
Financing fees incurred and deferred	0	(5,609)
Proceeds from issuance of notes payable	0	499,650
Repayment of notes payable	0	(413,252)
Repayment of loan payable	0	(100,000)
Net proceeds from amounts due under repurchase agreements	116,399	23,542
Proceeds from issuance of common stock	8,367	8,291
Change in checks in excess of cash balance	(19,626)	(8,687)
Net cash provided by financing activities	1,057,472	1,137,376
Increase (decrease) in cash and cash equivalents	(304,803)	494,396
Cash and cash equivalents at beginning of period	1,434,045	791,266
Cash and cash equivalents at end of period	1,129,242	1,285,662
Cash paid during period for interest:
Interest expense	24,009	39,583
Cash paid during period for income taxes:
Income taxes	148,157	109,581
Non-cash operating activity:
Deferral of sales inducements	$ 135,015	$ 175,076

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Consolidation and Basis of Presentation The accompanying consolidated financial statements of American Equity Investment Life Holding Company ("we", "us" or "our") have been prepared in accordance with U.S. generally accepted accounting principles ("GAAP") for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and notes required by GAAP for complete financial statements. The consolidated financial statements reflect all adjustments, consisting only of normal recurring items, which are necessary to present fairly our financial position and results of operations on a basis consistent with the prior audited consolidated financial statements. Operating results for the three and nine month periods ended September 30, 2018 are not necessarily indicative of the results that may be expected for the year ended December 31, 2018 . All significant intercompany accounts and transactions have been eliminated. The preparation of financial statements requires the use of management estimates. For further information related to a description of areas of judgment and estimates and other information necessary to understand our financial position and results of operations, refer to the audited consolidated financial statements and notes included in our Annual Report on Form 10-K for the year ended December 31, 2017 . Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued an accounting standards update ("ASU") related to revenue arising from contracts with customers. This ASU, which replaces most current revenue recognition guidance, including industry specific guidance, prescribes that an entity should recognize revenue to reflect the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. We adopted this ASU on January 1, 2018. The adoption of this ASU had no impact on our consolidated financial statements as revenues related to insurance contracts and investment contracts are excluded from its scope. In January 2016, the FASB issued an ASU that, among other aspects of recognition, measurement, presentation and disclosure of financial instruments, primarily requires equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. However, an entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. Additionally, it changes the accounting for financial liabilities measured at fair value under the fair value option and eliminates some disclosures regarding fair value of financial assets and liabilities measured at amortized cost. We adopted this ASU on January 1, 2018. The adoption of this ASU had no impact on our consolidated financial statements. In August 2016, the FASB issued an ASU that clarifies how certain cash receipts and cash payments are to be presented and classified in the statement of cash flows. We adopted this ASU on January 1, 2018. The adoption of this ASU resulted in a reclassification of certain cash flows related to equity method investment distributions from investing activities to operating activities within our consolidated statements of cash flows. In February 2018, the FASB issued an ASU that allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017 ("Tax Reform"). We adopted this ASU on January 1, 2018. The adoption of this ASU resulted in a reclassification of $128 million between accumulated other comprehensive income and retained earnings within our consolidated balance sheet. New Accounting Pronouncements In February 2016, the FASB issued an ASU that will require recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. This ASU affects accounting and disclosure more dramatically for lessees as accounting for lessors is mainly unchanged. This ASU will be effective for us on January 1, 2019, with early adoption permitted. While this guidance will lead to us establishing a lease asset and liability for our operating leases, we do not expect the impact to be significant to our consolidated financial statements. In June 2016, the FASB issued an ASU that significantly changes the impairment model for most financial assets that are measured at amortized cost and certain other instruments from an incurred loss model to an expected loss model that requires these assets be presented at the net amount expected to be collected. In addition, credit losses on available for sale debt securities should be recorded through an allowance account. This ASU will be effective for us on January 1, 2020, with early adoption permitted. While we are still in the process of evaluating the impact this guidance will have on our consolidated financial statements, we believe the new impairment model will lead to earlier recognition of credit losses for our commercial mortgage loans. In March 2017, the FASB issued an ASU that applies to certain callable debt securities where the amortized cost basis is at a premium to the price repayable by the issuer at the earliest call date. Under this guidance, the premium will be amortized to the first call date. This ASU will be effective for us on January 1, 2019, with early adoption permitted. We are in the process of evaluating the impact this guidance may have on our consolidated financial statements. In June 2018, the FASB issued an ASU that expands the scope of Accounting Standards Codification 718, Compensation-Stock Compensation, to include share-based payment transactions for acquiring goods and services to nonemployees and eliminates the existing accounting model for nonemployee share-based payment awards. This ASU will be effective for us on January 1, 2019, with early adoption permitted. While this guidance will lead to an earlier measurement date for our nonemployee restricted stock units that have not vested as of January 1, 2019, we do not expect it to have an impact on our consolidated financial statements upon adoption. In August 2018, the FASB issued an ASU that revises certain aspects of the measurement models and disclosure requirements for long duration insurance and investment contracts. The FASB’s objective in issuing this ASU is to improve, simplify, and enhance the accounting for long-duration contracts. The revisions include updating cash flow assumptions in the calculation of the liability for traditional life products, introducing the term ‘market risk benefit’ ("MRB") and requiring all contract features meeting the definition of an MRB to be measured at fair value, simplifying the method used to amortize deferred policy acquisition costs and deferred sales inducements to a constant basis over the expected term of the related contracts rather than based on gross profits and enhancing disclosure requirements. While this ASU is effective for us on January 1, 2021, the transition date (the remeasurement date) is January 1, 2019. Early adoption of this ASU is permitted. We are in process of evaluating the impact this guidance will have on our consolidated financial statements. Income Tax Reform As a result of Tax Reform, the federal corporate tax rate was reduced from 35% to 21% effective January 1, 2018.

Fair Values of Financial Instru

Fair Values of Financial Instruments	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Values of Financial Instruments	Fair Values of Financial Instruments The following sets forth a comparison of the carrying amounts and fair values of our financial instruments: September 30, 2018 December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value (Dollars in thousands) Assets Fixed maturity securities: Available for sale $ 45,822,017 $ 45,822,017 $ 45,372,989 $ 45,372,989 Held for investment 77,213 71,113 77,041 76,460 Mortgage loans on real estate 2,892,155 2,835,345 2,665,531 2,670,037 Derivative instruments 1,290,387 1,290,387 1,568,380 1,568,380 Other investments 536,594 528,867 616,764 605,894 Cash and cash equivalents 1,129,242 1,129,242 1,434,045 1,434,045 Coinsurance deposits 5,017,255 4,547,180 4,858,289 4,347,990 Interest rate caps 1,244 1,244 415 415 Interest rate swap 1,125 1,125 — — Counterparty collateral 179,512 179,512 186,108 186,108 Liabilities Policy benefit reserves 57,633,261 48,792,935 55,786,011 46,344,931 Single premium immediate annuity (SPIA) benefit reserves 271,275 279,993 282,563 292,153 Notes payable 494,464 500,000 494,093 521,800 Subordinated debentures 242,875 238,703 242,565 244,117 Amounts due under repurchase agreements 116,399 116,399 — — Interest rate swap — — 789 789 Fair value is the price that would be received to sell an asset or paid to transfer a liability (exit price) in an orderly transaction between market participants at the measurement date. The objective of a fair value measurement is to determine that price for each financial instrument at each measurement date. We meet this objective using various methods of valuation that include market, income and cost approaches. We categorize our financial instruments into three levels of fair value hierarchy based on the priority of inputs used in determining fair value. The hierarchy defines the highest priority inputs (Level 1) as quoted prices in active markets for identical assets or liabilities. The lowest priority inputs (Level 3) are our own assumptions about what a market participant would use in determining fair value such as estimated future cash flows. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, a financial instrument's level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the financial instrument. We categorize financial assets and liabilities recorded at fair value in the consolidated balance sheets as follows: Level 1— Quoted prices are available in active markets for identical financial instruments as of the reporting date. We do not adjust the quoted price for these financial instruments, even in situations where we hold a large position and a sale could reasonably impact the quoted price. Level 2— Quoted prices in active markets for similar financial instruments, quoted prices for identical or similar financial instruments in markets that are not active; and models and other valuation methodologies using inputs other than quoted prices that are observable. Level 3— Models and other valuation methodologies using significant inputs that are unobservable for financial instruments and include situations where there is little, if any, market activity for the financial instrument. The inputs into the determination of fair value require significant management judgment or estimation. Financial instruments that are included in Level 3 are securities for which no market activity or data exists and for which we used discounted expected future cash flows with our own assumptions about what a market participant would use in determining fair value. Transfers of securities among the levels occur at times and depend on the type of inputs used to determine fair value of each security. There were no transfers between levels during any period presented. Our assets and liabilities which are measured at fair value on a recurring basis as of September 30, 2018 and December 31, 2017 are presented below based on the fair value hierarchy levels: Total Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (Dollars in thousands) September 30, 2018 Assets Fixed maturity securities: Available for sale: United States Government full faith and credit $ 10,962 $ 5,454 $ 5,508 $ — United States Government sponsored agencies 1,224,587 — 1,224,587 — United States municipalities, states and territories 4,142,257 — 4,142,257 — Foreign government obligations 226,500 — 226,500 — Corporate securities 28,479,603 7 28,479,596 — Residential mortgage backed securities 1,181,682 — 1,181,682 — Commercial mortgage backed securities 5,337,368 — 5,337,368 — Other asset backed securities 5,219,058 — 5,219,058 — Other investments: equity securities 207,434 200,000 7,434 — Derivative instruments 1,290,387 — 1,290,387 — Cash and cash equivalents 1,129,242 1,129,242 — — Interest rate caps 1,244 — 1,244 — Interest rate swap 1,125 — 1,125 — Counterparty collateral 179,512 — 179,512 — $ 48,630,961 $ 1,334,703 $ 47,296,258 $ — Liabilities Fixed index annuities - embedded derivatives $ 8,947,193 $ — $ — $ 8,947,193 December 31, 2017 Assets Fixed maturity securities: Available for sale: United States Government full faith and credit $ 11,876 $ 5,640 $ 6,236 $ — United States Government sponsored agencies 1,305,017 — 1,305,017 — United States municipalities, states and territories 4,166,812 — 4,166,812 — Foreign government obligations 239,360 — 239,360 — Corporate securities 29,878,971 5 29,878,966 — Residential mortgage backed securities 1,105,567 — 1,105,567 — Commercial mortgage backed securities 5,544,850 — 5,544,850 — Other asset backed securities 3,120,536 — 3,120,536 — Other investments: equity securities, available for sale 292,429 285,000 7,429 — Derivative instruments 1,568,380 — 1,568,380 — Cash and cash equivalents 1,434,045 1,434,045 — — Interest rate caps 415 — 415 — Counterparty collateral 186,108 — 186,108 — $ 48,854,366 $ 1,724,690 $ 47,129,676 $ — Liabilities Interest rate swap $ 789 $ — $ 789 $ — Fixed index annuities - embedded derivatives 8,790,427 — — 8,790,427 $ 8,791,216 $ — $ 789 $ 8,790,427 The following methods and assumptions were used in estimating the fair values of financial instruments during the periods presented in these consolidated financial statements. Fixed maturity securities and equity securities The fair values of fixed maturity securities and equity securities in an active and orderly market are determined by utilizing independent pricing services. The independent pricing services incorporate a variety of observable market data in their valuation techniques, including: • reported trading prices, • benchmark yields, • broker-dealer quotes, • benchmark securities, • bids and offers, • credit ratings, • relative credit information, and • other reference data. The independent pricing services also take into account perceived market movements and sector news, as well as a security's terms and conditions, including any features specific to that issue that may influence risk and marketability. Depending on the security, the priority of the use of observable market inputs may change as some observable market inputs may not be relevant or additional inputs may be necessary. The independent pricing services provide quoted market prices when available. Quoted prices are not always available due to market inactivity. When quoted market prices are not available, the third parties use yield data and other factors relating to instruments or securities with similar characteristics to determine fair value for securities that are not actively traded. We generally obtain one value from our primary external pricing service. In situations where a price is not available from this service, we may obtain quotes or prices from additional parties as needed. Market indices of similar rated asset class spreads are considered for valuations and broker indications of similar securities are compared. Inputs used by the broker include market information, such as yield data and other factors relating to instruments or securities with similar characteristics. Valuations and quotes obtained from third party commercial pricing services are non-binding and do not represent quotes on which one may execute the disposition of the assets. We validate external valuations at least quarterly through a combination of procedures that include the evaluation of methodologies used by the pricing services, analytical reviews and performance analysis of the prices against trends, and maintenance of a securities watch list. Additionally, as needed we utilize discounted cash flow models or perform independent valuations on a case-by-case basis using inputs and assumptions similar to those used by the pricing services. Although we do identify differences from time to time as a result of these validation procedures, we did not make any significant adjustments as of September 30, 2018 and December 31, 2017 . Mortgage loans on real estate Mortgage loans on real estate are not measured at fair value on a recurring basis. The fair values of mortgage loans on real estate are calculated using discounted expected cash flows using competitive market interest rates currently being offered for similar loans. The fair values of impaired mortgage loans on real estate that we have considered to be collateral dependent are based on the fair value of the real estate collateral (based on appraised values) less estimated costs to sell. The inputs utilized to determine fair value of all mortgage loans are unobservable market data (competitive market interest rates); therefore, fair value of mortgage loans falls into Level 3 in the fair value hierarchy. Derivative instruments The fair values of derivative instruments, primarily call options, are based upon the amount of cash that we will receive to settle each derivative instrument on the reporting date. These amounts are determined by our investment team using industry accepted valuation models and are adjusted for the nonperformance risk of each counterparty net of any collateral held. Inputs include market volatility and risk free interest rates and are used in income valuation techniques in arriving at a fair value for each option contract. The nonperformance risk for each counterparty is based upon its credit default swap rate. We have no performance obligations related to the call options purchased to fund our fixed index annuity policy liabilities. Other investments Equity securities are the only financial instruments included in other investments that are measured at fair value on a recurring basis (see determination of fair value above). Financial instruments included in other investments that are not measured at fair value on a recurring basis are policy loans, equity method investments and company owned life insurance ("COLI"). We have not attempted to determine the fair values associated with our policy loans, as we believe any differences between carrying values and the fair values afforded these instruments are immaterial to our consolidated financial position and, accordingly, the cost to provide such disclosure does not justify the benefit to be derived. The fair values of our equity method investments are obtained from third parties and determined by calculating the present value of future cash flows discounted by a risk free rate, a risk spread and a liquidity discount. As the risk spread and liquidity discount are unobservable market inputs, the fair value of our equity method investments falls within Level 3 of the fair value hierarchy. The fair value of our COLI approximates the cash surrender value of the policies and falls within Level 2 of the fair value hierarchy. Cash and cash equivalents Amounts reported in the consolidated balance sheets for these instruments are reported at their historical cost which approximates fair value due to the nature of the assets assigned to this category. Interest rate swap and caps The fair values of our pay fixed/receive variable interest rate swap and our interest rate caps are obtained from third parties and are determined by discounting expected future cash flows using a projected London Interbank Offered Rate ("LIBOR") for the term of the swap and caps. Counterparty collateral Amounts reported in other assets in the consolidated balance sheets for these instruments are reported at their historical cost which approximates fair value due to the nature of the assets assigned to this category. Policy benefit reserves, coinsurance deposits and SPIA benefit reserves The fair values of the liabilities under contracts not involving significant mortality or morbidity risks (principally deferred annuities), are stated at the cost we would incur to extinguish the liability (i.e., the cash surrender value) as these contracts are generally issued without an annuitization date. The coinsurance deposits related to the annuity benefit reserves have fair values determined in a similar fashion. For period-certain annuity benefit contracts, the fair value is determined by discounting the benefits at the interest rates currently in effect for newly issued immediate annuity contracts. We are not required to and have not estimated the fair value of the liabilities under contracts that involve significant mortality or morbidity risks, as these liabilities fall within the definition of insurance contracts that are exceptions from financial instruments that require disclosures of fair value. Policy benefit reserves, coinsurance deposits and SPIA benefit reserves are not measured at fair value on a recurring basis. All of the fair values presented within these categories fall within Level 3 of the fair value hierarchy as most of the inputs are unobservable market data. Notes payable The fair values of our senior unsecured notes are based upon pricing matrices developed by a third party pricing service when quoted market prices are not available and are categorized as Level 2 within the fair value hierarchy. Notes payable are not remeasured at fair value on a recurring basis. Subordinated debentures Fair values for subordinated debentures are estimated using discounted cash flow calculations based principally on observable inputs including our incremental borrowing rates, which reflect our credit rating, for similar types of borrowings with maturities consistent with those remaining for the debt being valued. These fair values are categorized as Level 2 within the fair value hierarchy. Subordinated debentures are not measured at fair value on a recurring basis. Amounts due under repurchase agreements The amounts reported in the consolidated balance sheets for short term indebtedness under repurchase agreements with variable interest rates approximate their fair values. Fixed index annuities - embedded derivatives We estimate the fair value of the embedded derivative component of our fixed index annuity policy benefit reserves at each valuation date by (i) projecting policy contract values and minimum guaranteed contract values over the expected lives of the contracts and (ii) discounting the excess of the projected contract value amounts at the applicable risk free interest rates adjusted for our nonperformance risk related to those liabilities. The projections of policy contract values are based on our best estimate assumptions for future policy growth and future policy decrements. Our best estimate assumptions for future policy growth include assumptions for the expected index credit on the next policy anniversary date which are derived from the fair values of the underlying call options purchased to fund such index credits and the expected costs of annual call options we will purchase in the future to fund index credits beyond the next policy anniversary. The projections of minimum guaranteed contract values include the same best estimate assumptions for policy decrements as were used to project policy contract values. Within this determination we have the following significant unobservable inputs: 1) the expected cost of annual call options we will purchase in the future to fund index credits beyond the next policy anniversary and 2) our best estimates for future policy decrements, primarily lapse, partial withdrawal and mortality rates. As of September 30, 2018 and December 31, 2017 , we utilized an estimate of 3.10% for the expected cost of annual call options, which is based on estimated long-term account value growth and a historical review of our actual option costs. Our best estimate assumptions for lapse, partial withdrawal and mortality rates are based on our actual experience and our outlook as to future expectations for such assumptions. These assumptions, which are consistent with the assumptions used in calculating deferred policy acquisition costs and deferred sales inducements, are reviewed on a quarterly basis and are revised as our experience develops and/or as future expectations change. Our mortality rate assumptions are based on 65% of the 1983 Basic Annuity Mortality Tables. The following table presents average lapse rate and partial withdrawal rate assumptions, by contract duration, used in estimating the fair value of the embedded derivative component of our fixed index annuity policy benefit reserves at each reporting date: Average Lapse Rates Average Partial Withdrawal Rates Contract Duration (Years) September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 1 - 5 2.05% 1.83% 3.33% 3.32% 6 - 10 7.28% 7.01% 3.33% 3.32% 11 - 15 11.35% 11.31% 3.35% 3.34% 16 - 20 11.91% 11.96% 3.21% 3.20% 20+ 11.58% 11.62% 3.21% 3.20% Lapse rates are generally expected to increase as surrender charge percentages decrease. Lapse expectations reflect a significant increase in the year in which the surrender charge period on a contract ends. The following table provides a reconciliation of the beginning and ending balances for our Level 3 liabilities, which are measured at fair value on a recurring basis using significant unobservable inputs for the three and nine months ended September 30, 2018 and 2017 : Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands) Fixed index annuities - embedded derivatives Beginning balance $ 8,351,151 $ 7,552,365 $ 8,790,427 $ 6,563,288 Premiums less benefits 399,234 475,600 1,354,881 1,384,791 Change in fair value, net 196,808 41,140 (1,198,115 ) 121,026 Ending balance $ 8,947,193 $ 8,069,105 $ 8,947,193 $ 8,069,105 The fair value of our fixed index annuities embedded derivatives is net of coinsurance ceded of $592.6 million and $539.7 million as of September 30, 2018 and December 31, 2017 , respectively. Change in fair value, net for each period in our embedded derivatives is included in change in fair value of embedded derivatives in the unaudited consolidated statements of operations. Certain derivatives embedded in our fixed index annuity contracts are our most significant financial instrument measured at fair value that are categorized as Level 3 in the fair value hierarchy. The contractual obligations for future annual index credits within our fixed index annuity contracts are treated as a "series of embedded derivatives" over the expected life of the applicable contracts. We estimate the fair value of these embedded derivatives at each valuation date by the method described above under fixed index annuities - embedded derivatives . The projections of minimum guaranteed contract values include the same best estimate assumptions for policy decrements as were used to project policy contract values. The most sensitive assumption in determining policy liabilities for fixed index annuities is the rates used to discount the excess projected contract values. As indicated above, the discount rate reflects our nonperformance risk. If the discount rates used to discount the excess projected contract values at September 30, 2018 , were to increase by 100 basis points, the fair value of the embedded derivatives would decrease by $553.9 million recorded through operations as a decrease in the change in fair value of embedded derivatives and there would be a corresponding decrease of $330.2 million to our combined balance for deferred policy acquisition costs and deferred sales inducements recorded through operations as an increase in amortization of deferred policy acquisition costs and deferred sales inducements. A decrease by 100 basis points in the discount rate used to discount the excess projected contract values would increase the fair value of the embedded derivatives by $614.7 million recorded through operations as an increase in the change in fair value of embedded derivatives and there would be a corresponding increase of $352.1 million to our combined balance for deferred policy acquisition costs and deferred sales inducements recorded through operations as a decrease in amortization of deferred policy acquisition costs and deferred sales inducements.

Investments

Investments	9 Months Ended
	Sep. 30, 2018
Investments [Abstract]
Investments	Investments At September 30, 2018 and December 31, 2017 , the amortized cost and fair value of fixed maturity securities were as follows: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) September 30, 2018 Fixed maturity securities: Available for sale: United States Government full faith and credit $ 11,528 $ 79 $ (645 ) $ 10,962 United States Government sponsored agencies 1,308,358 11,824 (95,595 ) 1,224,587 United States municipalities, states and territories 3,949,293 224,586 (31,622 ) 4,142,257 Foreign government obligations 226,931 7,240 (7,671 ) 226,500 Corporate securities 28,406,182 746,913 (673,492 ) 28,479,603 Residential mortgage backed securities 1,129,176 64,183 (11,677 ) 1,181,682 Commercial mortgage backed securities 5,434,044 22,684 (119,360 ) 5,337,368 Other asset backed securities 5,222,830 35,553 (39,325 ) 5,219,058 $ 45,688,342 $ 1,113,062 $ (979,387 ) $ 45,822,017 Held for investment: Corporate security $ 77,213 $ — $ (6,100 ) $ 71,113 December 31, 2017 Fixed maturity securities: Available for sale: United States Government full faith and credit $ 11,861 $ 162 $ (147 ) $ 11,876 United States Government sponsored agencies 1,308,290 28,457 (31,730 ) 1,305,017 United States municipalities, states and territories 3,804,360 366,048 (3,596 ) 4,166,812 Foreign government obligations 228,214 13,171 (2,025 ) 239,360 Corporate securities 28,127,653 1,897,005 (145,687 ) 29,878,971 Residential mortgage backed securities 1,028,484 79,554 (2,471 ) 1,105,567 Commercial mortgage backed securities 5,531,922 82,768 (69,840 ) 5,544,850 Other asset backed securities 3,075,975 57,966 (13,405 ) 3,120,536 $ 43,116,759 $ 2,525,131 $ (268,901 ) $ 45,372,989 Held for investment: Corporate security $ 77,041 $ — $ (581 ) $ 76,460 Other investments: equity securities, available for sale: Finance, insurance, and real estate $ 292,429 $ — $ — $ 292,429 The amortized cost and fair value of fixed maturity securities at September 30, 2018 , by contractual maturity, are shown below. Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. All of our mortgage and other asset backed securities provide for periodic payments throughout their lives and are shown below as separate lines. Available for sale Held for investment Amortized Cost Fair Value Amortized Cost Fair Value (Dollars in thousands) Due in one year or less $ 283,309 $ 287,677 $ — $ — Due after one year through five years 5,564,840 5,561,473 — — Due after five years through ten years 9,893,201 9,753,983 — — Due after ten years through twenty years 9,562,224 9,883,734 — — Due after twenty years 8,598,718 8,597,042 77,213 71,113 33,902,292 34,083,909 77,213 71,113 Residential mortgage backed securities 1,129,176 1,181,682 — — Commercial mortgage backed securities 5,434,044 5,337,368 — — Other asset backed securities 5,222,830 5,219,058 — — $ 45,688,342 $ 45,822,017 $ 77,213 $ 71,113 Net unrealized gains on available for sale fixed maturity securities reported as a separate component of stockholders' equity were comprised of the following: September 30, 2018 December 31, 2017 (Dollars in thousands) Net unrealized gains on available for sale fixed maturity securities $ 133,675 $ 2,256,230 Adjustments for assumed changes in amortization of deferred policy acquisition costs and deferred sales inducements (73,225 ) (1,206,078 ) Deferred income tax valuation allowance reversal 22,534 22,534 Deferred income tax expense (a) (12,696 ) (348,087 ) Net unrealized gains reported as accumulated other comprehensive income $ 70,288 $ 724,599 (a) December 31, 2017 includes $128 million related to the impact of Tax Reform that was reclassified between accumulated other comprehensive income and retained earnings within our consolidated balance sheet during the first quarter of 2018. For more information regarding the reclassification, see Note 1 to our unaudited consolidated financial statements. The National Association of Insurance Commissioners ("NAIC") assigns designations to fixed maturity securities. These designations range from Class 1 (highest quality) to Class 6 (lowest quality). In general, securities are assigned a designation based upon the ratings they are given by Nationally Recognized Statistical Rating Organizations ("NRSRO’s"). The NAIC designations are utilized by insurers in preparing their annual statutory statements. NAIC Class 1 and 2 designations are considered "investment grade" while NAIC Class 3 through 6 designations are considered "non-investment grade." Based on the NAIC designations, we had 97% of our fixed maturity portfolio rated investment grade at both September 30, 2018 and December 31, 2017 , respectively. The following table summarizes the credit quality, as determined by NAIC designation, of our fixed maturity portfolio as of the dates indicated: September 30, 2018 December 31, 2017 NAIC Designation Amortized Cost Fair Value Amortized Cost Fair Value (Dollars in thousands) 1 $ 27,186,979 $ 27,478,961 $ 26,669,427 $ 28,274,379 2 16,972,448 16,868,800 15,198,551 15,869,219 3 1,406,867 1,365,147 1,161,737 1,157,420 4 180,233 156,449 134,838 117,542 5 11,200 16,898 17,015 20,927 6 7,828 6,875 12,232 9,962 $ 45,765,555 $ 45,893,130 $ 43,193,800 $ 45,449,449 The following table shows our investments' gross unrealized losses and fair value, aggregated by investment category and length of time that individual securities (consisting of 2,630 and 955 securities, respectively) have been in a continuous unrealized loss position, at September 30, 2018 and December 31, 2017 : Less than 12 months 12 months or more Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses (Dollars in thousands) September 30, 2018 Fixed maturity securities: Available for sale: United States Government full faith and credit $ 3,178 $ (98 ) $ 5,989 $ (547 ) $ 9,167 $ (645 ) United States Government sponsored agencies 43,310 (2,770 ) 927,678 (92,825 ) 970,988 (95,595 ) United States municipalities, states and territories 684,699 (21,142 ) 123,625 (10,480 ) 808,324 (31,622 ) Foreign government obligations 106,283 (4,031 ) 60,641 (3,640 ) 166,924 (7,671 ) Corporate securities: Finance, insurance and real estate 2,825,957 (83,452 ) 783,568 (75,867 ) 3,609,525 (159,319 ) Manufacturing, construction and mining 2,145,542 (70,140 ) 294,755 (26,064 ) 2,440,297 (96,204 ) Utilities and related sectors 2,569,490 (87,914 ) 383,587 (34,057 ) 2,953,077 (121,971 ) Wholesale/retail trade 1,026,417 (36,525 ) 143,605 (18,263 ) 1,170,022 (54,788 ) Services, media and other 4,472,035 (135,921 ) 950,004 (105,289 ) 5,422,039 (241,210 ) Residential mortgage backed securities 396,096 (9,620 ) 41,760 (2,057 ) 437,856 (11,677 ) Commercial mortgage backed securities 2,423,197 (40,541 ) 1,610,912 (78,819 ) 4,034,109 (119,360 ) Other asset backed securities 3,066,340 (27,693 ) 191,639 (11,632 ) 3,257,979 (39,325 ) $ 19,762,544 $ (519,847 ) $ 5,517,763 $ (459,540 ) $ 25,280,307 $ (979,387 ) Held for investment: Corporate security: Insurance $ — $ — $ 71,113 $ (6,100 ) $ 71,113 $ (6,100 ) December 31, 2017 Fixed maturity securities: Available for sale: United States Government full faith and credit $ 1,565 $ (10 ) $ 6,731 $ (137 ) $ 8,296 $ (147 ) United States Government sponsored agencies 44,794 (180 ) 958,965 (31,550 ) 1,003,759 (31,730 ) United States municipalities, states and territories 44,736 (128 ) 128,499 (3,468 ) 173,235 (3,596 ) Foreign government obligations 49,663 (337 ) 12,625 (1,688 ) 62,288 (2,025 ) Corporate securities: Finance, insurance and real estate 456,244 (5,135 ) 600,655 (28,043 ) 1,056,899 (33,178 ) Manufacturing, construction and mining 222,985 (3,475 ) 231,196 (10,849 ) 454,181 (14,324 ) Utilities and related sectors 395,183 (4,099 ) 249,416 (8,901 ) 644,599 (13,000 ) Wholesale/retail trade 152,941 (1,249 ) 178,635 (11,371 ) 331,576 (12,620 ) Services, media and other 729,124 (19,000 ) 891,654 (53,565 ) 1,620,778 (72,565 ) Residential mortgage backed securities 39,771 (387 ) 32,917 (2,084 ) 72,688 (2,471 ) Commercial mortgage backed securities 1,096,757 (10,385 ) 1,306,437 (59,455 ) 2,403,194 (69,840 ) Other asset backed securities 765,531 (3,499 ) 217,595 (9,906 ) 983,126 (13,405 ) $ 3,999,294 $ (47,884 ) $ 4,815,325 $ (221,017 ) $ 8,814,619 $ (268,901 ) Held for investment: Corporate security: Insurance $ — $ — $ 76,460 $ (581 ) $ 76,460 $ (581 ) Based on the results of our process for evaluating available for sale securities in unrealized loss positions for other than temporary impairments, which is discussed in detail later in this footnote, we have determined that the unrealized losses on the securities in the preceding table are temporary. The unrealized losses at September 30, 2018 are principally related to timing of the purchases of these securities, which carry less yield than those available at September 30, 2018 . Approximately 93% and 83% of the unrealized losses on fixed maturity securities shown in the above table for September 30, 2018 and December 31, 2017 , respectively, are on securities that are rated investment grade, defined as being the highest two NAIC designations. All of the fixed maturity securities with unrealized losses are current with respect to the payment of principal and interest. Changes in net unrealized gains on investments for the three and nine months ended September 30, 2018 and 2017 are as follows: Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands) Fixed maturity securities held for investment carried at amortized cost $ 2,947 $ (1,711 ) $ (5,519 ) $ 6,119 Investments carried at fair value: Fixed maturity securities, available for sale $ (311,954 ) $ 128,981 $ (2,122,555 ) $ 1,008,483 Equity securities, available for sale — (457 ) — (479 ) (311,954 ) 128,524 (2,122,555 ) 1,008,004 Adjustment for effect on other balance sheet accounts: Deferred policy acquisition costs and deferred sales inducements 172,566 (52,572 ) 1,132,853 (516,427 ) Deferred income tax asset/liability 29,270 (26,583 ) 207,837 (172,052 ) 201,836 (79,155 ) 1,340,690 (688,479 ) Change in net unrealized gains on investments carried at fair value $ (110,118 ) $ 49,369 $ (781,865 ) $ 319,525 Proceeds from sales of available for sale securities for the nine months ended September 30, 2018 and 2017 were $1.8 billion and $496.1 million , respectively. Scheduled principal repayments, calls and tenders for available for sale fixed maturity securities for the nine months ended September 30, 2018 and 2017 were $997.6 million and $837.7 million , respectively. Realized gains and losses on sales are determined on the basis of specific identification of investments based on the trade date. Net realized gains (losses) on investments, excluding net OTTI losses for the three and nine months ended September 30, 2018 and 2017 , are as follows: Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands) Available for sale fixed maturity securities: Gross realized gains $ 505 $ 1,520 $ 2,845 $ 11,571 Gross realized losses (1,913 ) (1 ) (43,648 ) (4,463 ) (1,408 ) 1,519 (40,803 ) 7,108 Available for sale equity securities: Gross realized gains — 348 — 348 Other investments: Gain on sale of real estate — 12 — 56 Mortgage loans on real estate: Decrease (increase) in allowance for credit losses (1,255 ) (300 ) (785 ) 278 Recovery of specific allowance 467 — 1,189 — Gain on sale of mortgage loans — — 124 — (788 ) (300 ) 528 278 $ (2,196 ) $ 1,579 $ (40,275 ) $ 7,790 Losses on available for sale fixed maturity securities were realized primarily due to strategies to reposition the fixed maturity security portfolio that result in improved net investment income, credit risk or duration profiles as they pertain to our asset liability management. We review and analyze all investments on an ongoing basis for changes in market interest rates and credit deterioration. This review process includes analyzing our ability to recover the amortized cost basis of each investment that has a fair value that is materially lower than its amortized cost and requires a high degree of management judgment and involves uncertainty. The evaluation of securities for other than temporary impairments is a quantitative and qualitative process, which is subject to risks and uncertainties. We have a policy and process to identify securities that could potentially have impairments that are other than temporary. This process involves monitoring market events and other items that could impact issuers. The evaluation includes but is not limited to such factors as: • the length of time and the extent to which the fair value has been less than amortized cost or cost; • whether the issuer is current on all payments and all contractual payments have been made as agreed; • the remaining payment terms and the financial condition and near-term prospects of the issuer; • the lack of ability to refinance due to liquidity problems in the credit market; • the fair value of any underlying collateral; • the existence of any credit protection available; • our intent to sell and whether it is more likely than not we would be required to sell prior to recovery for debt securities; • consideration of rating agency actions; and • changes in estimated cash flows of mortgage and asset backed securities. We determine whether other than temporary impairment losses should be recognized for debt securities by assessing all facts and circumstances surrounding each security. Where the decline in fair value of debt securities is attributable to changes in market interest rates or to factors such as market volatility, liquidity and spread widening, and we anticipate recovery of all contractual or expected cash flows, we do not consider these investments to be other than temporarily impaired because we do not intend to sell these investments and it is not more likely than not we will be required to sell these investments before a recovery of amortized cost, which may be maturity. If we intend to sell a debt security or if it is more likely than not that we will be required to sell a debt security before recovery of its amortized cost basis, other than temporary impairment has occurred and the difference between amortized cost and fair value will be recognized as a loss in operations. If we do not intend to sell and it is not more likely than not we will be required to sell the debt security but also do not expect to recover the entire amortized cost basis of the security, an impairment loss would be recognized in operations in the amount of the expected credit loss. We determine the amount of expected credit loss by calculating the present value of the cash flows expected to be collected discounted at each security's acquisition yield based on our consideration of whether the security was of high credit quality at the time of acquisition. The difference between the present value of expected future cash flows and the amortized cost basis of the security is the amount of credit loss recognized in operations. The remaining amount of the other than temporary impairment is recognized in other comprehensive income (loss). The determination of the credit loss component of a mortgage backed security is based on a number of factors. The primary consideration in this evaluation process is the issuer's ability to meet current and future interest and principal payments as contractually stated at time of purchase. Our review of these securities includes an analysis of the cash flow modeling under various default scenarios considering independent third party benchmarks, the seniority of the specific tranche within the structure of the security, the composition of the collateral and the actual default, loss severity and prepayment experience exhibited. With the input of third party assumptions for default projections, loss severity and prepayment expectations, we evaluate the cash flow projections to determine whether the security is performing in accordance with its contractual obligation. We utilize the models from a leading structured product software specialist serving institutional investors. These models incorporate each security's seniority and cash flow structure. In circumstances where the analysis implies a potential for principal loss at some point in the future, we use the "best estimate" cash flow projection discounted at the security's effective yield at acquisition to determine the amount of our potential credit loss associated with this security. The discounted expected future cash flows equates to our expected recovery value. Any shortfall of the expected recovery when compared to the amortized cost of the security will be recorded as the credit loss component of other than temporary impairment. The cash flow modeling is performed on a security-by-security basis and incorporates actual cash flows on the residential mortgage backed securities through the current period, as well as the projection of remaining cash flows using a number of assumptions including default rates, prepayment rates and loss severity rates. The default curves we use are tailored to the Prime or Alt-A residential mortgage backed securities that we own, which assume lower default rates and loss severity for Prime securities versus Alt-A securities. These default curves are scaled higher or lower depending on factors such as current underlying mortgage loan performance, rating agency loss projections, loan to value ratios, geographic diversity, as well as other appropriate considerations. The following table presents the range of significant assumptions used to determine the credit loss component of other than temporary impairments we have recognized on residential mortgage backed securities for the nine months ended September 30, 2018 and 2017 , which are all senior level tranches within the structure of the securities: Discount Rate Default Rate Loss Severity Vintage Min Max Min Max Min Max Nine months ended September 30, 2018 Prime 2005 7.0 % 7.7 % 14 % 23 % 40 % 50 % 2007 6.6 % 6.6 % 17 % 17 % 60 % 60 % Nine months ended September 30, 2017 Prime 2005 7.0 % 7.7 % 8 % 22 % 40 % 50 % 2006 7.3 % 7.3 % 14 % 14 % 40 % 40 % 2007 6.2 % 6.6 % 15 % 19 % 50 % 60 % The determination of the credit loss component of a corporate bond (including redeemable preferred stocks) is based on the underlying financial performance of the issuer and their ability to meet their contractual obligations. Considerations in our evaluation include, but are not limited to, credit rating changes, financial statement and ratio analysis, changes in management, significant changes in credit spreads, breaches of financial covenants and a review of the economic outlook for the industry and markets in which they trade. In circumstances where an issuer appears unlikely to meet its future obligation, or the security's price decline is deemed other than temporary, an estimate of credit loss is determined. Credit loss is calculated using default probabilities as derived from the credit default swaps markets in conjunction with recovery rates derived from independent third party analysis or a best estimate of credit loss. This credit loss rate is then incorporated into a present value calculation based on an expected principal loss in the future discounted at the yield at the date of purchase and compared to amortized cost to determine the amount of credit loss associated with the security. In addition, for debt securities which we do not intend to sell and it is not more likely than not we will be required to sell, but our intent changes due to changes or events that could not have been reasonably anticipated, an other than temporary impairment charge is recognized. Once an impairment charge has been recorded, we then continue to review the other than temporarily impaired securities for appropriate valuation on an ongoing basis. Unrealized losses may be recognized in future periods through a charge to earnings should we later conclude that the decline in fair value below amortized cost is other than temporary pursuant to our accounting policy described above. The use of different methodologies and assumptions to determine the fair value of investments and the timing and amount of impairments may have a material effect on the amounts presented in our consolidated financial statements. The following table summarizes other than temporary impairments for the three and nine months ended September 30, 2018 and 2017 , by asset type: Number of Securities Total OTTI Losses Portion of OTTI Losses Recognized in (from) Other Comprehensive Income Net OTTI Losses Recognized in Operations (Dollars in thousands) Three months ended September 30, 2018 Fixed maturity securities, available for sale: Corporate securities: Capital goods 1 $ (719 ) $ — $ (719 ) Consumer discretionary 6 (5,968 ) — (5,968 ) Energy 2 (1,212 ) — (1,212 ) Financials 5 (3,495 ) — (3,495 ) Information technology 1 (550 ) — (550 ) Telecommunications 2 (249 ) — (249 ) Transportation 1 (178 ) — (178 ) Utilities 1 (94 ) — (94 ) Commercial mortgage backed securities 1 (1,908 ) — (1,908 ) 20 $ (14,373 ) $ — $ (14,373 ) Three months ended September 30, 2017 Fixed maturity securities, available for sale: Residential mortgage backed securities 3 $ (273 ) $ (191 ) $ (464 ) Nine months ended September 30, 2018 Fixed maturity securities, available for sale: Corporate securities: Capital goods 1 $ (719 ) $ — $ (719 ) Consumer discretionary 7 (6,875 ) — (6,875 ) Energy 2 (1,212 ) — (1,212 ) Financials 5 (3,495 ) — (3,495 ) Information technology 1 (550 ) — (550 ) Telecommunications 2 (249 ) — (249 ) Transportation 1 (178 ) — (178 ) Utilities 1 (94 ) — (94 ) Residential mortgage backed securities 3 (63 ) (295 ) (358 ) Commercial mortgage backed securities 1 (1,908 ) — (1,908 ) Other asset backed securities 1 (682 ) (1,356 ) (2,038 ) 25 $ (16,025 ) $ (1,651 ) $ (17,676 ) Nine months ended September 30, 2017 Fixed maturity securities, available for sale: Residential mortgage backed securities 8 $ (273 ) $ (994 ) $ (1,267 ) Other asset backed securities 1 — (287 ) (287 ) 9 $ (273 ) $ (1,281 ) $ (1,554 ) The cumulative portion of other than temporary impairments determined to be credit losses which have been recognized in operations for debt securities are summarized as follows: Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands) Cumulative credit loss at beginning of period $ (156,469 ) $ (153,526 ) $ (157,066 ) $ (166,375 ) Additions for the amount related to credit losses for which OTTI has not previously been recognized (14,373 ) (273 ) (16,025 ) (273 ) Additional credit losses on securities for which OTTI has previously been recognized — (191 ) (1,651 ) (1,281 ) Accumulated losses on securities that were disposed of during the period — — 3,900 13,939 Cumulative credit loss at end of period $ (170,842 ) $ (153,990 ) $ (170,842 ) $ (153,990 ) The following table summarizes the cumulative noncredit portion of OTTI and the change in fair value since recognition of OTTI, both of which were recognized in other comprehensive income, by major type of security, for securities that are part of our investment portfolio at September 30, 2018 and December 31, 2017 : Amortized Cost OTTI Recognized in Other Comprehensive Income Change in Fair Value Since OTTI was Recognized Fair Value (Dollars in thousands) September 30, 2018 Fixed maturity securities, available for sale: Corporate securities $ 389,729 $ (3,700 ) $ 10,041 $ 396,070 Residential mortgage backed securities 255,611 (168,060 ) 202,923 290,474 Commercial mortgage backed securities 7,823 — — 7,823 Other asset backed securities 2,529 — (1,682 ) 847 $ 655,692 $ (171,760 ) $ 211,282 $ 695,214 December 31, 2017 Fixed maturity securities, available for sale: Corporate securities $ 13,015 $ (4,263 ) $ 10,739 $ 19,491 Residential mortgage backed securities 297,582 (168,355 ) 201,620 330,847 Other asset backed securities 4,567 (1,356 ) (1,875 ) 1,336 $ 315,164 $ (173,974 ) $ 210,484 $ 351,674

Mortgage Loans on Real Estate

Mortgage Loans on Real Estate	9 Months Ended
	Sep. 30, 2018
Mortgage Loans on Real Estate [Abstract]
Mortgage Loans on Real Estate	Mortgage Loans on Real Estate Our mortgage loan portfolio is summarized in the following table. There were commitments outstanding of $58.5 million at September 30, 2018 . September 30, 2018 December 31, 2017 (Dollars in thousands) Principal outstanding $ 2,900,458 $ 2,674,315 Loan loss allowance (7,114 ) (7,518 ) Deferred prepayment fees (1,189 ) (1,266 ) Carrying value $ 2,892,155 $ 2,665,531 The portfolio consists of commercial mortgage loans collateralized by the related properties and diversified as to property type, location and loan size. Our mortgage lending policies establish limits on the amount that can be loaned to one borrower and other criteria to attempt to reduce the risk of default. The mortgage loan portfolio is summarized by geographic region and property type as follows: September 30, 2018 December 31, 2017 Principal Percent Principal Percent (Dollars in thousands) Geographic distribution East $ 598,239 20.6 % $ 548,067 20.5 % Middle Atlantic 170,836 5.9 % 163,485 6.1 % Mountain 348,233 12.0 % 308,486 11.5 % New England 9,482 0.3 % 12,265 0.5 % Pacific 494,791 17.1 % 466,030 17.4 % South Atlantic 667,043 23.0 % 609,736 22.8 % West North Central 309,332 10.7 % 324,808 12.2 % West South Central 302,502 10.4 % 241,438 9.0 % $ 2,900,458 100.0 % $ 2,674,315 100.0 % Property type distribution Office $ 267,017 9.2 % $ 283,926 10.6 % Medical Office 33,950 1.2 % 34,338 1.3 % Retail 1,076,573 37.1 % 1,040,028 38.9 % Industrial/Warehouse 743,787 25.7 % 677,770 25.3 % Apartment 604,120 20.8 % 462,897 17.3 % Mixed use/other 175,011 6.0 % 175,356 6.6 % $ 2,900,458 100.0 % $ 2,674,315 100.0 % Our financing receivables currently consist of one portfolio segment which is our commercial mortgage loan portfolio. These are mortgage loans with collateral consisting of commercial real estate and borrowers consisting mostly of limited liability partnerships or limited liability corporations. We evaluate our mortgage loan portfolio for the establishment of a loan loss allowance by specific identification of impaired loans and the measurement of an estimated loss for each individual loan identified. A mortgage loan is impaired when it is probable that we will be unable to collect all amounts due according to the contractual terms of the loan agreement. If we determine that the value of any specific mortgage loan is impaired, the carrying amount of the mortgage loan will be reduced to its fair value, based upon the present value of expected future cash flows from the loan discounted at the loan's effective interest rate, or the fair value of the underlying collateral less estimated costs to sell. In addition, we analyze the mortgage loan portfolio for the need of a general loan allowance for probable losses on all other loans on a quantitative and qualitative basis. The amount of the general loan allowance is based upon management's evaluation of the collectability of the loan portfolio, historical loss experience, delinquencies, credit concentrations, underwriting standards and national and local economic conditions. We rate each of the mortgage loans in our portfolio based on factors such as historical operating performance, loan to value ratio and economic outlook, among others. We calculate a loss factor to apply to each rating based on historical losses we have recognized in our mortgage loan portfolio. We apply the loss factors to the total principal outstanding within each rating category to determine an appropriate estimate of the general loan loss allowance. We also assess the portfolio qualitatively and apply a loss rate to all loans without a specific allowance based on management's assessment of economic conditions, and we apply an additional amount of loss allowance to a group of loans that we have identified as having higher risk of loss. The following table presents a rollforward of our specific and general valuation allowances for mortgage loans on real estate: Three Months Ended Three Months Ended Specific Allowance General Allowance Specific Allowance General Allowance (Dollars in thousands) Beginning allowance balance $ (696 ) $ (5,630 ) $ (2,049 ) $ (5,800 ) Charge-offs — — — — Recoveries 467 — — — Change in provision for credit losses (1,255 ) — — (300 ) Ending allowance balance $ (1,484 ) $ (5,630 ) $ (2,049 ) $ (6,100 ) Nine Months Ended Nine Months Ended Specific Allowance General Allowance Specific Allowance General Allowance (Dollars in thousands) Beginning allowance balance $ (1,418 ) $ (6,100 ) $ (1,327 ) $ (7,100 ) Charge-offs — — — — Recoveries 1,189 — — — Change in provision for credit losses (1,255 ) 470 (722 ) 1,000 Ending allowance balance $ (1,484 ) $ (5,630 ) $ (2,049 ) $ (6,100 ) The specific allowance represents the total credit loss allowances on loans which are individually evaluated for impairment. The general allowance is for the group of loans discussed above which are collectively evaluated for impairment. The following table presents the total outstanding principal of loans evaluated for impairment by basis of impairment method: September 30, 2018 December 31, 2017 (Dollars in thousands) Individually evaluated for impairment $ 3,179 $ 5,445 Collectively evaluated for impairment 2,897,279 2,668,870 Total loans evaluated for impairment $ 2,900,458 $ 2,674,315 Charge-offs include allowances that have been established on loans that were satisfied either by taking ownership of the collateral or by some other means such as discounted pay-off or loan sale. When ownership of the property is taken it is recorded at the lower of the mortgage loan's carrying value or the property's fair value (based on appraised values) less estimated costs to sell. The real estate owned is recorded as a component of Other investments and the mortgage loan is recorded as fully paid, with any allowance for credit loss that has been established charged off. Fair value of the real estate is determined by third party appraisal. Recoveries are situations where we have received a payment from the borrower in an amount greater than the carrying value of the loan (principal outstanding less specific allowance). We did not own any real estate during the three and nine months ended September 30, 2018 and 2017. We analyze credit risk of our mortgage loans by analyzing all available evidence on loans that are delinquent and loans that are in a workout period. September 30, 2018 December 31, 2017 (Dollars in thousands) Credit Exposure - By Payment Activity Performing $ 2,898,538 $ 2,670,657 In workout — 1,436 Collateral dependent 1,920 2,222 $ 2,900,458 $ 2,674,315 The loans that are categorized as "in workout" consist of loans that we have agreed to lower or no mortgage payments for a period of time while the borrowers address cash flow and/or operational issues. The key features of these workouts have been determined on a loan-by-loan basis. Most of these loans are in a period of low cash flow due to tenants vacating their space or tenants requesting rent relief during difficult economic periods. Generally, we have allowed the borrower a six month interest only period and in some cases a twelve month period of interest only. Interest only workout loans are expected to return to their regular debt service payments after the interest only period. Interest only loans that are not fully amortizing will have a larger balance at their balloon date than originally contracted. Fully amortizing loans that are in interest only periods will have larger debt service payments for their remaining term due to lost principal payments during the interest only period. In limited circumstances we have allowed borrowers to pay the principal portion of their loan payment into an escrow account that can be used for capital and tenant improvements for a period of not more than twelve months. In these situations new loan amortization schedules are calculated based on the principal not collected during this twelve month workout period and larger payments are collected for the remaining term of each loan. In all cases, the original interest rate and maturity date have not been modified, and we have not forgiven any principal amounts. Mortgage loans are considered delinquent when they become 60 days or more past due. In general, when loans become 90 days past due, become collateral dependent or enter a period with no debt service payments required we place them on non-accrual status and discontinue recognizing interest income. If payments are received on a delinquent loan, interest income is recognized to the extent it would have been recognized if normal principal and interest would have been received timely. If payments are received to bring a delinquent loan back to current we will resume accruing interest income on that loan. There were $1.9 million and $2.2 million loans in non-accrual status at September 30, 2018 and December 31, 2017 , respectively. We define collateral dependent loans as those mortgage loans for which we will depend on the value of the collateral real estate to satisfy the outstanding principal of the loan. All of our commercial mortgage loans depend on the cash flow of the borrower to be at a sufficient level to service the principal and interest payments as they come due. In general, cash inflows of the borrowers are generated by collecting monthly rent from tenants occupying space within the borrowers' properties. Our borrowers face collateral risks such as tenants going out of business, tenants struggling to make rent payments as they become due, and tenants canceling leases and moving to other locations. We have a number of loans where the real estate is occupied by a single tenant. Our borrowers sometimes face both a reduction in cash flow on their mortgage property as well as a reduction in the fair value of the real estate collateral. If borrowers are unable to replace lost rent revenue and increases in the fair value of their property do not materialize, we could potentially incur more losses than what we have allowed for in our specific and general loan loss allowances. Aging of financing receivables is summarized in the following table, with loans in a "workout" period as of the reporting date considered current if payments are current in accordance with agreed upon terms: 30 - 59 Days 60 - 89 Days 90 Days and Over Total Past Due Current Collateral Dependent Receivables Total Financing Receivables (Dollars in thousands) Commercial Mortgage Loans September 30, 2018 $ — $ — $ — $ — $ 2,898,538 $ 1,920 $ 2,900,458 December 31, 2017 $ — $ — $ — $ — $ 2,672,093 $ 2,222 $ 2,674,315 Financing receivables summarized in the following two tables represent all loans that we are either not currently collecting, or those we feel it is probable we will not collect all amounts due according to the contractual terms of the loan agreements (all loans that we have worked with the borrower to alleviate short-term cash flow issues, loans delinquent for 60 days or more at the reporting date, loans we have determined to be collateral dependent and loans that we have recorded specific impairments on that we feel may continue to have performance issues). Recorded Investment Unpaid Principal Balance Related Allowance (Dollars in thousands) September 30, 2018 Mortgage loans with an allowance $ 1,695 $ 3,179 $ (1,484 ) Mortgage loans with no related allowance — — — $ 1,695 $ 3,179 $ (1,484 ) December 31, 2017 Mortgage loans with an allowance $ 4,027 $ 5,445 $ (1,418 ) Mortgage loans with no related allowance 1,436 1,436 — $ 5,463 $ 6,881 $ (1,418 ) Average Recorded Investment Interest Income Recognized (Dollars in thousands) Three months ended September 30, 2018 Mortgage loans with an allowance $ 2,337 $ 37 Mortgage loans with no related allowance — — $ 2,337 $ 37 Three months ended September 30, 2017 Mortgage loans with an allowance $ 4,702 $ 21 Mortgage loans with no related allowance 1,496 22 $ 6,198 $ 43 Nine months ended September 30, 2018 Mortgage loans with an allowance $ 2,386 $ 136 Mortgage loans with no related allowance — — $ 2,386 $ 136 Nine months ended September 30, 2017 Mortgage loans with an allowance $ 5,112 $ 228 Mortgage loans with no related allowance 1,533 69 $ 6,645 $ 297 A Troubled Debt Restructuring ("TDR") is a situation where we have granted a concession to a borrower for economic or legal reasons related to the borrower's financial difficulties that we would not otherwise consider. A mortgage loan that has been granted new terms, including workout terms as described previously, would be considered a TDR if it meets conditions that would indicate a borrower is experiencing financial difficulty and the new terms constitute a concession on our part. We analyze all loans where we have agreed to workout terms and all loans that we have refinanced to determine if they meet the definition of a TDR. We consider the following factors in determining whether or not a borrower is experiencing financial difficulty: • borrower is in default, • borrower has declared bankruptcy, • there is growing concern about the borrower's ability to continue as a going concern, • borrower has insufficient cash flows to service debt, • borrower's inability to obtain funds from other sources, and • there is a breach of financial covenants by the borrower. If the borrower is determined to be in financial difficulty, we consider the following conditions to determine if the borrower is granted a concession: • assets used to satisfy debt are less than our recorded investment, • interest rate is modified, • maturity date extension at an interest rate less than market rate, • capitalization of interest, • delaying principal and/or interest for a period of three months or more, and • partial forgiveness of the balance or charge-off. Mortgage loan workouts, refinances or restructures that are classified as TDRs are individually evaluated and measured for impairment. There were no mortgage loans on commercial real estate that we determined to be a TDR at September 30, 2018. A summary of mortgage loans on commercial real estate with outstanding principal at December 31, 2017 that we determined to be TDRs are as follows: Geographic Region Number of TDRs Principal Balance Outstanding Specific Loan Loss Allowance Net Carrying Amount (Dollars in thousands) December 31, 2017 South Atlantic 1 $ 2,947 $ — $ 2,947 East 1 1,933 (467 ) 1,466 2 $ 4,880 $ (467 ) $ 4,413

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments None of our derivatives qualify for hedge accounting, thus, any change in the fair value of the derivatives is recognized immediately in the consolidated statements of operations. The fair value of our derivative instruments, including derivative instruments embedded in fixed index annuity contracts, presented in the consolidated balance sheets are as follows: September 30, 2018 December 31, 2017 (Dollars in thousands) Assets Derivative instruments Call options $ 1,290,387 $ 1,568,380 Other assets Interest rate caps 1,244 415 Interest rate swap 1,125 — $ 1,292,756 $ 1,568,795 Liabilities Policy benefit reserves - annuity products Fixed index annuities - embedded derivatives $ 8,947,193 $ 8,790,427 Other liabilities Interest rate swap — 789 $ 8,947,193 $ 8,791,216 The changes in fair value of derivatives included in the unaudited consolidated statements of operations are as follows: Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands) Change in fair value of derivatives: Call options $ 594,872 $ 362,560 $ 273,946 $ 1,017,001 Interest rate swap 258 63 1,658 (411 ) Interest rate caps 181 (98 ) 829 (712 ) $ 595,311 $ 362,525 $ 276,433 $ 1,015,878 Change in fair value of embedded derivatives: Fixed index annuities - embedded derivatives $ 196,808 $ 41,140 $ (1,198,115 ) $ 121,026 Other changes in difference between policy benefit reserves computed using derivative accounting vs. long-duration contracts accounting 186,908 188,562 612,650 507,819 $ 383,716 $ 229,702 $ (585,465 ) $ 628,845 The amounts presented as "Other changes in difference between policy benefit reserves computed using derivative accounting vs. long-duration contracts accounting" represents the total change in the difference between policy benefit reserves for fixed index annuities computed under the derivative accounting standard and the long-duration contracts accounting standard at each balance sheet date, less the change in fair value of our fixed index annuities embedded derivatives that is presented as Level 3 liabilities in Note 2. We have fixed index annuity products that guarantee the return of principal to the policyholder and credit interest based on a percentage of the gain in a specified market index. When fixed index annuity deposits are received, a portion of the deposit is used to purchase derivatives consisting of call options on the applicable market indices to fund the index credits due to fixed index annuity policyholders. Substantially all such call options are one year options purchased to match the funding requirements of the underlying policies. The call options are marked to fair value with the change in fair value included as a component of revenues. The change in fair value of derivatives includes the gains or losses recognized at the expiration of the option term or upon early termination and the changes in fair value for open positions. On the respective anniversary dates of the index policies, the index used to compute the annual index credit is reset and we purchase new one -year call options to fund the next annual index credit. We manage the cost of these purchases through the terms of our fixed index annuities, which permit us to change caps, participation rates, and/or asset fees, subject to guaranteed minimums on each policy's anniversary date. By adjusting caps, participation rates, or asset fees, we can generally manage option costs except in cases where the contractual features would prevent further modifications. Our strategy attempts to mitigate any potential risk of loss due to the nonperformance of the counterparties to these call options through a regular monitoring process which evaluates the program's effectiveness. We do not purchase call options that would require payment or collateral to another institution and our call options do not contain counterparty credit-risk-related contingent features. We are exposed to risk of loss in the event of nonperformance by the counterparties and, accordingly, we purchase our option contracts from multiple counterparties and evaluate the creditworthiness of all counterparties prior to purchase of the contracts. All of these options have been purchased from nationally recognized financial institutions with a Standard and Poor's credit rating of A- or higher at the time of purchase and the maximum credit exposure to any single counterparty is subject to concentration limits. We also have credit support agreements that allow us to request the counterparty to provide collateral to us when the fair value of our exposure to the counterparty exceeds specified amounts. The notional amount and fair value of our call options by counterparty and each counterparty's current credit rating are as follows: September 30, 2018 December 31, 2017 Counterparty Credit Rating (S&P) Credit Rating (Moody's) Notional Amount Fair Value Notional Amount Fair Value (Dollars in thousands) Bank of America A+ Aa3 $ 6,215,626 $ 214,380 $ 4,645,366 $ 237,955 Barclays A A2 2,509,716 76,397 4,135,537 154,127 BNP Paribas A Aa3 — — 1,411,989 73,650 Canadian Imperial Bank of Commerce A+ Aa2 5,200,352 173,803 2,808,030 84,268 Citibank, N.A. A+ A1 4,904,171 176,825 4,104,666 219,900 Credit Suisse A A1 2,640,799 62,867 3,538,855 137,384 J.P. Morgan A+ Aa3 3,225,810 116,332 1,753,649 109,689 Morgan Stanley A+ A1 3,941,705 124,691 3,408,179 184,323 Royal Bank of Canada AA- A2 1,942,305 67,105 3,027,469 104,141 Societe Generale A A1 1,769,787 53,835 — — SunTrust A- Baa1 1,644,816 54,149 2,331,168 90,399 Wells Fargo A+ Aa2 4,659,622 163,569 4,036,255 162,781 Exchange traded 235,663 6,434 296,840 9,763 $ 38,890,372 $ 1,290,387 $ 35,498,003 $ 1,568,380 As of September 30, 2018 and December 31, 2017 , we held $1.3 billion and $1.6 billion , respectively, of cash and cash equivalents and other securities from counterparties for derivative collateral, which is included in Other liabilities on our consolidated balance sheets. This derivative collateral limits the maximum amount of economic loss due to credit risk that we would incur if parties to the call options failed completely to perform according to the terms of the contracts to $18.8 million and $11.9 million at September 30, 2018 and December 31, 2017 , respectively. The future annual index credits on our fixed index annuities are treated as a "series of embedded derivatives" over the expected life of the applicable contract. We do not purchase call options to fund the index liabilities which may arise after the next policy anniversary date. We must value both the call options and the related forward embedded options in the policies at fair value. We entered into an interest rate swap and interest rate caps to manage interest rate risk associated with the floating rate component on certain of our subordinated debentures. See Note 10 in our Annual Report on Form 10-K for the year ended December 31, 2017 for more information on our subordinated debentures. The terms of the interest rate swap provide that we pay a fixed rate of interest and receive a floating rate of interest. The terms of the interest rate caps limit the three month LIBOR to 2.50% . The interest rate swap and caps are not effective hedges under accounting guidance for derivative instruments and hedging activities. Therefore, we record the interest rate swap and caps at fair value and any net cash payments received or paid are included in the change in fair value of derivatives in the unaudited consolidated statements of operations. Details regarding the interest rate swap are as follows: Notional Pay September 30, 2018 December 31, 2017 Maturity Date Amount Receive Rate Rate Counterparty Fair Value (Dollars in thousands) March 15, 2021 $ 85,500 LIBOR 2.415 % SunTrust $ 1,125 $ (789 ) Details regarding the interest rate caps are as follows: Notional Cap September 30, 2018 December 31, 2017 Maturity Date Amount Floating Rate Rate Counterparty Fair Value (Dollars in thousands) July 7, 2021 $ 40,000 LIBOR 2.50 % SunTrust $ 624 $ 207 July 8, 2021 12,000 LIBOR 2.50 % SunTrust 187 62 July 29, 2021 27,000 LIBOR 2.50 % SunTrust 433 146 $ 79,000 $ 1,244 $ 415 The interest rate swap converts floating rates to fixed rates for seven years which began in March 2014. The interest rate caps cap our interest rates for seven years which began in July 2014.

Notes Payable and Amounts Due U

Notes Payable and Amounts Due Under Repurchase Agreements	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Notes Payable and Amounts Due Under Repurchase Agreements	Notes Payable and Amounts Due Under Repurchase Agreements Notes payable includes the following: September 30, 2018 December 31, 2017 (Dollars in thousands) Senior notes due 2027 Principal $ 500,000 $ 500,000 Unamortized debt issue costs (5,222 ) (5,572 ) Unamortized discount (314 ) (335 ) $ 494,464 $ 494,093 On June 16, 2017, we issued $500 million aggregate principal amount of senior unsecured notes due 2027 which bear interest at 5.0% per year and will mature on June 15, 2027 (the "2027 Notes"). The 2027 Notes were issued at a $0.3 million discount, which is being amortized over the term of the 2027 Notes using the effective interest method. Contractual interest is payable semi-annually in arrears each June 15th and December 15th. The initial transaction fees and costs totaling $5.8 million were capitalized as deferred financing costs and are being amortized over the term of the 2027 Notes using the effective interest method. As part of our investment strategy, we enter into securities repurchase agreements (short-term collateralized borrowings). When we do borrow cash on these repurchase agreements, we pledge collateral in the form of debt securities with fair values approximately equal to the amount due and we use the cash to purchase debt securities ahead of the time we collect the cash from selling annuity policies to avoid a lag between the investment of funds and the obligation to credit interest to policyholders. We earn investment income on the securities purchased with these borrowings at a rate in excess of the cost of these borrowings. Such borrowings averaged $5.1 million and $41.4 million during the three and nine months ended September 30, 2018 , respectively, compared to $22.4 million and $53.3 million for the same periods in 2017 . The maximum amount borrowed was $544.1 million and $274.5 million during the nine months ended September 30, 2018 and 2017 , respectively. The weighted average interest rate on amounts due under repurchase agreements was 0.00% and 1.66% for the three and nine months ended September 30, 2018 , respectively, compared to 1.35% and 0.83% for the same periods in 2017 .

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies We are occasionally involved in litigation, both as a defendant and as a plaintiff. In addition, state regulatory bodies, such as state insurance departments, the Securities and Exchange Commission ("SEC"), Financial Industry Regulatory Authority, the Department of Labor ("DOL"), and other regulatory bodies regularly make inquiries and conduct examinations or investigations concerning our compliance with, among other things, insurance laws, securities laws, the Employee Retirement Income Security Act of 1974, as amended, and laws governing the activities of broker/dealers. In accordance with applicable accounting guidelines, we establish an accrued liability for litigation and regulatory matters when those matters present loss contingencies that are both probable and estimable. As a litigation or regulatory matter is developing we, in conjunction with outside counsel, evaluate on an ongoing basis whether the matter presents a loss contingency that meets conditions indicating the need for accrual and/or disclosure, and if not the matter will continue to be monitored for further developments. If and when the loss contingency related to litigation or regulatory matters is deemed to be both probable and estimable, we will establish an accrued liability with respect to that matter and will continue to monitor the matter for further developments that may affect the amount of the accrued liability. There can be no assurance that any pending or future litigation will not have a material adverse effect on our business, financial condition, or results of operations. In addition to our commitments to fund mortgage loans, we have unfunded commitments at September 30, 2018 to limited partnerships of $47.3 million and to privately placed corporate securities of $60.0 million .

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Earnings Per Share The following table sets forth the computation of earnings per common share and earnings per common share - assuming dilution: Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands, except share and per share data) Numerator: Net income - numerator for earnings per common share $ 169,328 $ 56,957 $ 404,193 $ 137,842 Denominator: Weighted average common shares outstanding 90,485,567 89,068,770 90,278,209 88,872,562 Effect of dilutive securities: Stock options and deferred compensation agreements 705,465 974,208 750,588 924,465 Restricted stock and restricted stock units 459,854 377,552 326,613 373,993 Denominator for earnings per common share - assuming dilution 91,650,886 90,420,530 91,355,410 90,171,020 Earnings per common share $ 1.87 $ 0.64 $ 4.48 $ 1.55 Earnings per common share - assuming dilution $ 1.85 $ 0.63 $ 4.42 $ 1.53 There were no options to purchase shares of our common stock outstanding excluded from the computation of diluted earnings per share during the three and nine months ended September 30, 2018 or 2017 , as the exercise price of all options outstanding was less than the average market price of our common shares for those periods.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Adopted and New Accounting Pronouncements, Policy	Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued an accounting standards update ("ASU") related to revenue arising from contracts with customers. This ASU, which replaces most current revenue recognition guidance, including industry specific guidance, prescribes that an entity should recognize revenue to reflect the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. We adopted this ASU on January 1, 2018. The adoption of this ASU had no impact on our consolidated financial statements as revenues related to insurance contracts and investment contracts are excluded from its scope. In January 2016, the FASB issued an ASU that, among other aspects of recognition, measurement, presentation and disclosure of financial instruments, primarily requires equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. However, an entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. Additionally, it changes the accounting for financial liabilities measured at fair value under the fair value option and eliminates some disclosures regarding fair value of financial assets and liabilities measured at amortized cost. We adopted this ASU on January 1, 2018. The adoption of this ASU had no impact on our consolidated financial statements. In August 2016, the FASB issued an ASU that clarifies how certain cash receipts and cash payments are to be presented and classified in the statement of cash flows. We adopted this ASU on January 1, 2018. The adoption of this ASU resulted in a reclassification of certain cash flows related to equity method investment distributions from investing activities to operating activities within our consolidated statements of cash flows. In February 2018, the FASB issued an ASU that allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017 ("Tax Reform"). We adopted this ASU on January 1, 2018. The adoption of this ASU resulted in a reclassification of $128 million between accumulated other comprehensive income and retained earnings within our consolidated balance sheet. New Accounting Pronouncements In February 2016, the FASB issued an ASU that will require recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. This ASU affects accounting and disclosure more dramatically for lessees as accounting for lessors is mainly unchanged. This ASU will be effective for us on January 1, 2019, with early adoption permitted. While this guidance will lead to us establishing a lease asset and liability for our operating leases, we do not expect the impact to be significant to our consolidated financial statements. In June 2016, the FASB issued an ASU that significantly changes the impairment model for most financial assets that are measured at amortized cost and certain other instruments from an incurred loss model to an expected loss model that requires these assets be presented at the net amount expected to be collected. In addition, credit losses on available for sale debt securities should be recorded through an allowance account. This ASU will be effective for us on January 1, 2020, with early adoption permitted. While we are still in the process of evaluating the impact this guidance will have on our consolidated financial statements, we believe the new impairment model will lead to earlier recognition of credit losses for our commercial mortgage loans. In March 2017, the FASB issued an ASU that applies to certain callable debt securities where the amortized cost basis is at a premium to the price repayable by the issuer at the earliest call date. Under this guidance, the premium will be amortized to the first call date. This ASU will be effective for us on January 1, 2019, with early adoption permitted. We are in the process of evaluating the impact this guidance may have on our consolidated financial statements. In June 2018, the FASB issued an ASU that expands the scope of Accounting Standards Codification 718, Compensation-Stock Compensation, to include share-based payment transactions for acquiring goods and services to nonemployees and eliminates the existing accounting model for nonemployee share-based payment awards. This ASU will be effective for us on January 1, 2019, with early adoption permitted. While this guidance will lead to an earlier measurement date for our nonemployee restricted stock units that have not vested as of January 1, 2019, we do not expect it to have an impact on our consolidated financial statements upon adoption. In August 2018, the FASB issued an ASU that revises certain aspects of the measurement models and disclosure requirements for long duration insurance and investment contracts. The FASB’s objective in issuing this ASU is to improve, simplify, and enhance the accounting for long-duration contracts. The revisions include updating cash flow assumptions in the calculation of the liability for traditional life products, introducing the term ‘market risk benefit’ ("MRB") and requiring all contract features meeting the definition of an MRB to be measured at fair value, simplifying the method used to amortize deferred policy acquisition costs and deferred sales inducements to a constant basis over the expected term of the related contracts rather than based on gross profits and enhancing disclosure requirements. While this ASU is effective for us on January 1, 2021, the transition date (the remeasurement date) is January 1, 2019. Early adoption of this ASU is permitted. We are in process of evaluating the impact this guidance will have on our consolidated financial statements. Income Tax Reform As a result of Tax Reform, the federal corporate tax rate was reduced from 35% to 21% effective January 1, 2018.
Fair Values of Financial Instruments, Policy	Fair value is the price that would be received to sell an asset or paid to transfer a liability (exit price) in an orderly transaction between market participants at the measurement date. The objective of a fair value measurement is to determine that price for each financial instrument at each measurement date. We meet this objective using various methods of valuation that include market, income and cost approaches. We categorize our financial instruments into three levels of fair value hierarchy based on the priority of inputs used in determining fair value. The hierarchy defines the highest priority inputs (Level 1) as quoted prices in active markets for identical assets or liabilities. The lowest priority inputs (Level 3) are our own assumptions about what a market participant would use in determining fair value such as estimated future cash flows. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, a financial instrument's level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the financial instrument. We categorize financial assets and liabilities recorded at fair value in the consolidated balance sheets as follows: Level 1— Quoted prices are available in active markets for identical financial instruments as of the reporting date. We do not adjust the quoted price for these financial instruments, even in situations where we hold a large position and a sale could reasonably impact the quoted price. Level 2— Quoted prices in active markets for similar financial instruments, quoted prices for identical or similar financial instruments in markets that are not active; and models and other valuation methodologies using inputs other than quoted prices that are observable. Level 3— Models and other valuation methodologies using significant inputs that are unobservable for financial instruments and include situations where there is little, if any, market activity for the financial instrument. The inputs into the determination of fair value require significant management judgment or estimation. Financial instruments that are included in Level 3 are securities for which no market activity or data exists and for which we used discounted expected future cash flows with our own assumptions about what a market participant would use in determining fair value. Transfers of securities among the levels occur at times and depend on the type of inputs used to determine fair value of each security.
Investments, Policy	We review and analyze all investments on an ongoing basis for changes in market interest rates and credit deterioration. This review process includes analyzing our ability to recover the amortized cost basis of each investment that has a fair value that is materially lower than its amortized cost and requires a high degree of management judgment and involves uncertainty. The evaluation of securities for other than temporary impairments is a quantitative and qualitative process, which is subject to risks and uncertainties. We have a policy and process to identify securities that could potentially have impairments that are other than temporary. This process involves monitoring market events and other items that could impact issuers. The evaluation includes but is not limited to such factors as: • the length of time and the extent to which the fair value has been less than amortized cost or cost; • whether the issuer is current on all payments and all contractual payments have been made as agreed; • the remaining payment terms and the financial condition and near-term prospects of the issuer; • the lack of ability to refinance due to liquidity problems in the credit market; • the fair value of any underlying collateral; • the existence of any credit protection available; • our intent to sell and whether it is more likely than not we would be required to sell prior to recovery for debt securities; • consideration of rating agency actions; and • changes in estimated cash flows of mortgage and asset backed securities. We determine whether other than temporary impairment losses should be recognized for debt securities by assessing all facts and circumstances surrounding each security. Where the decline in fair value of debt securities is attributable to changes in market interest rates or to factors such as market volatility, liquidity and spread widening, and we anticipate recovery of all contractual or expected cash flows, we do not consider these investments to be other than temporarily impaired because we do not intend to sell these investments and it is not more likely than not we will be required to sell these investments before a recovery of amortized cost, which may be maturity. If we intend to sell a debt security or if it is more likely than not that we will be required to sell a debt security before recovery of its amortized cost basis, other than temporary impairment has occurred and the difference between amortized cost and fair value will be recognized as a loss in operations. If we do not intend to sell and it is not more likely than not we will be required to sell the debt security but also do not expect to recover the entire amortized cost basis of the security, an impairment loss would be recognized in operations in the amount of the expected credit loss. We determine the amount of expected credit loss by calculating the present value of the cash flows expected to be collected discounted at each security's acquisition yield based on our consideration of whether the security was of high credit quality at the time of acquisition. The difference between the present value of expected future cash flows and the amortized cost basis of the security is the amount of credit loss recognized in operations. The remaining amount of the other than temporary impairment is recognized in other comprehensive income (loss). The determination of the credit loss component of a mortgage backed security is based on a number of factors. The primary consideration in this evaluation process is the issuer's ability to meet current and future interest and principal payments as contractually stated at time of purchase. Our review of these securities includes an analysis of the cash flow modeling under various default scenarios considering independent third party benchmarks, the seniority of the specific tranche within the structure of the security, the composition of the collateral and the actual default, loss severity and prepayment experience exhibited. With the input of third party assumptions for default projections, loss severity and prepayment expectations, we evaluate the cash flow projections to determine whether the security is performing in accordance with its contractual obligation. We utilize the models from a leading structured product software specialist serving institutional investors. These models incorporate each security's seniority and cash flow structure. In circumstances where the analysis implies a potential for principal loss at some point in the future, we use the "best estimate" cash flow projection discounted at the security's effective yield at acquisition to determine the amount of our potential credit loss associated with this security. The discounted expected future cash flows equates to our expected recovery value. Any shortfall of the expected recovery when compared to the amortized cost of the security will be recorded as the credit loss component of other than temporary impairment. The cash flow modeling is performed on a security-by-security basis and incorporates actual cash flows on the residential mortgage backed securities through the current period, as well as the projection of remaining cash flows using a number of assumptions including default rates, prepayment rates and loss severity rates. The default curves we use are tailored to the Prime or Alt-A residential mortgage backed securities that we own, which assume lower default rates and loss severity for Prime securities versus Alt-A securities. These default curves are scaled higher or lower depending on factors such as current underlying mortgage loan performance, rating agency loss projections, loan to value ratios, geographic diversity, as well as other appropriate considerations. The determination of the credit loss component of a corporate bond (including redeemable preferred stocks) is based on the underlying financial performance of the issuer and their ability to meet their contractual obligations. Considerations in our evaluation include, but are not limited to, credit rating changes, financial statement and ratio analysis, changes in management, significant changes in credit spreads, breaches of financial covenants and a review of the economic outlook for the industry and markets in which they trade. In circumstances where an issuer appears unlikely to meet its future obligation, or the security's price decline is deemed other than temporary, an estimate of credit loss is determined. Credit loss is calculated using default probabilities as derived from the credit default swaps markets in conjunction with recovery rates derived from independent third party analysis or a best estimate of credit loss. This credit loss rate is then incorporated into a present value calculation based on an expected principal loss in the future discounted at the yield at the date of purchase and compared to amortized cost to determine the amount of credit loss associated with the security. In addition, for debt securities which we do not intend to sell and it is not more likely than not we will be required to sell, but our intent changes due to changes or events that could not have been reasonably anticipated, an other than temporary impairment charge is recognized. Once an impairment charge has been recorded, we then continue to review the other than temporarily impaired securities for appropriate valuation on an ongoing basis. Unrealized losses may be recognized in future periods through a charge to earnings should we later conclude that the decline in fair value below amortized cost is other than temporary pursuant to our accounting policy described above. The use of different methodologies and assumptions to determine the fair value of investments and the timing and amount of impairments may have a material effect on the amounts presented in our consolidated financial statements.
Mortgage Loans on Real Estate, Allowance for Loan Losses, Policy	We evaluate our mortgage loan portfolio for the establishment of a loan loss allowance by specific identification of impaired loans and the measurement of an estimated loss for each individual loan identified. A mortgage loan is impaired when it is probable that we will be unable to collect all amounts due according to the contractual terms of the loan agreement. If we determine that the value of any specific mortgage loan is impaired, the carrying amount of the mortgage loan will be reduced to its fair value, based upon the present value of expected future cash flows from the loan discounted at the loan's effective interest rate, or the fair value of the underlying collateral less estimated costs to sell. In addition, we analyze the mortgage loan portfolio for the need of a general loan allowance for probable losses on all other loans on a quantitative and qualitative basis. The amount of the general loan allowance is based upon management's evaluation of the collectability of the loan portfolio, historical loss experience, delinquencies, credit concentrations, underwriting standards and national and local economic conditions. We rate each of the mortgage loans in our portfolio based on factors such as historical operating performance, loan to value ratio and economic outlook, among others. We calculate a loss factor to apply to each rating based on historical losses we have recognized in our mortgage loan portfolio. We apply the loss factors to the total principal outstanding within each rating category to determine an appropriate estimate of the general loan loss allowance. We also assess the portfolio qualitatively and apply a loss rate to all loans without a specific allowance based on management's assessment of economic conditions, and we apply an additional amount of loss allowance to a group of loans that we have identified as having higher risk of loss.
Mortgage Loans on Real Estate, Real Estate Acquired Through Foreclosure, Policy	Charge-offs include allowances that have been established on loans that were satisfied either by taking ownership of the collateral or by some other means such as discounted pay-off or loan sale. When ownership of the property is taken it is recorded at the lower of the mortgage loan's carrying value or the property's fair value (based on appraised values) less estimated costs to sell. The real estate owned is recorded as a component of Other investments and the mortgage loan is recorded as fully paid, with any allowance for credit loss that has been established charged off. Fair value of the real estate is determined by third party appraisal. Recoveries are situations where we have received a payment from the borrower in an amount greater than the carrying value of the loan (principal outstanding less specific allowance).
Mortgage Loans on Real Estate, Non-Accrual Loan Status, Policy	The loans that are categorized as "in workout" consist of loans that we have agreed to lower or no mortgage payments for a period of time while the borrowers address cash flow and/or operational issues. The key features of these workouts have been determined on a loan-by-loan basis. Most of these loans are in a period of low cash flow due to tenants vacating their space or tenants requesting rent relief during difficult economic periods. Generally, we have allowed the borrower a six month interest only period and in some cases a twelve month period of interest only. Interest only workout loans are expected to return to their regular debt service payments after the interest only period. Interest only loans that are not fully amortizing will have a larger balance at their balloon date than originally contracted. Fully amortizing loans that are in interest only periods will have larger debt service payments for their remaining term due to lost principal payments during the interest only period. In limited circumstances we have allowed borrowers to pay the principal portion of their loan payment into an escrow account that can be used for capital and tenant improvements for a period of not more than twelve months. In these situations new loan amortization schedules are calculated based on the principal not collected during this twelve month workout period and larger payments are collected for the remaining term of each loan. In all cases, the original interest rate and maturity date have not been modified, and we have not forgiven any principal amounts. Mortgage loans are considered delinquent when they become 60 days or more past due. In general, when loans become 90 days past due, become collateral dependent or enter a period with no debt service payments required we place them on non-accrual status and discontinue recognizing interest income. If payments are received on a delinquent loan, interest income is recognized to the extent it would have been recognized if normal principal and interest would have been received timely. If payments are received to bring a delinquent loan back to current we will resume accruing interest income on that loan.
Mortgage Loans on Real Estate, Troubled Debt Restructuring, Policy	A Troubled Debt Restructuring ("TDR") is a situation where we have granted a concession to a borrower for economic or legal reasons related to the borrower's financial difficulties that we would not otherwise consider. A mortgage loan that has been granted new terms, including workout terms as described previously, would be considered a TDR if it meets conditions that would indicate a borrower is experiencing financial difficulty and the new terms constitute a concession on our part. We analyze all loans where we have agreed to workout terms and all loans that we have refinanced to determine if they meet the definition of a TDR. We consider the following factors in determining whether or not a borrower is experiencing financial difficulty: • borrower is in default, • borrower has declared bankruptcy, • there is growing concern about the borrower's ability to continue as a going concern, • borrower has insufficient cash flows to service debt, • borrower's inability to obtain funds from other sources, and • there is a breach of financial covenants by the borrower. If the borrower is determined to be in financial difficulty, we consider the following conditions to determine if the borrower is granted a concession: • assets used to satisfy debt are less than our recorded investment, • interest rate is modified, • maturity date extension at an interest rate less than market rate, • capitalization of interest, • delaying principal and/or interest for a period of three months or more, and • partial forgiveness of the balance or charge-off. Mortgage loan workouts, refinances or restructures that are classified as TDRs are individually evaluated and measured for impairment.
Commitments and Contingencies, Policy	In accordance with applicable accounting guidelines, we establish an accrued liability for litigation and regulatory matters when those matters present loss contingencies that are both probable and estimable. As a litigation or regulatory matter is developing we, in conjunction with outside counsel, evaluate on an ongoing basis whether the matter presents a loss contingency that meets conditions indicating the need for accrual and/or disclosure, and if not the matter will continue to be monitored for further developments. If and when the loss contingency related to litigation or regulatory matters is deemed to be both probable and estimable, we will establish an accrued liability with respect to that matter and will continue to monitor the matter for further developments that may affect the amount of the accrued liability.

Fair Values of Financial Inst_2

Fair Values of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Carrying Amounts and Fair Values of Financial Instruments	The following sets forth a comparison of the carrying amounts and fair values of our financial instruments: September 30, 2018 December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value (Dollars in thousands) Assets Fixed maturity securities: Available for sale $ 45,822,017 $ 45,822,017 $ 45,372,989 $ 45,372,989 Held for investment 77,213 71,113 77,041 76,460 Mortgage loans on real estate 2,892,155 2,835,345 2,665,531 2,670,037 Derivative instruments 1,290,387 1,290,387 1,568,380 1,568,380 Other investments 536,594 528,867 616,764 605,894 Cash and cash equivalents 1,129,242 1,129,242 1,434,045 1,434,045 Coinsurance deposits 5,017,255 4,547,180 4,858,289 4,347,990 Interest rate caps 1,244 1,244 415 415 Interest rate swap 1,125 1,125 — — Counterparty collateral 179,512 179,512 186,108 186,108 Liabilities Policy benefit reserves 57,633,261 48,792,935 55,786,011 46,344,931 Single premium immediate annuity (SPIA) benefit reserves 271,275 279,993 282,563 292,153 Notes payable 494,464 500,000 494,093 521,800 Subordinated debentures 242,875 238,703 242,565 244,117 Amounts due under repurchase agreements 116,399 116,399 — — Interest rate swap — — 789 789
Assets and Liabilities Measured at Fair Value on a Recurring Basis, By Fair Value Hierarchy Level	Our assets and liabilities which are measured at fair value on a recurring basis as of September 30, 2018 and December 31, 2017 are presented below based on the fair value hierarchy levels: Total Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (Dollars in thousands) September 30, 2018 Assets Fixed maturity securities: Available for sale: United States Government full faith and credit $ 10,962 $ 5,454 $ 5,508 $ — United States Government sponsored agencies 1,224,587 — 1,224,587 — United States municipalities, states and territories 4,142,257 — 4,142,257 — Foreign government obligations 226,500 — 226,500 — Corporate securities 28,479,603 7 28,479,596 — Residential mortgage backed securities 1,181,682 — 1,181,682 — Commercial mortgage backed securities 5,337,368 — 5,337,368 — Other asset backed securities 5,219,058 — 5,219,058 — Other investments: equity securities 207,434 200,000 7,434 — Derivative instruments 1,290,387 — 1,290,387 — Cash and cash equivalents 1,129,242 1,129,242 — — Interest rate caps 1,244 — 1,244 — Interest rate swap 1,125 — 1,125 — Counterparty collateral 179,512 — 179,512 — $ 48,630,961 $ 1,334,703 $ 47,296,258 $ — Liabilities Fixed index annuities - embedded derivatives $ 8,947,193 $ — $ — $ 8,947,193 December 31, 2017 Assets Fixed maturity securities: Available for sale: United States Government full faith and credit $ 11,876 $ 5,640 $ 6,236 $ — United States Government sponsored agencies 1,305,017 — 1,305,017 — United States municipalities, states and territories 4,166,812 — 4,166,812 — Foreign government obligations 239,360 — 239,360 — Corporate securities 29,878,971 5 29,878,966 — Residential mortgage backed securities 1,105,567 — 1,105,567 — Commercial mortgage backed securities 5,544,850 — 5,544,850 — Other asset backed securities 3,120,536 — 3,120,536 — Other investments: equity securities, available for sale 292,429 285,000 7,429 — Derivative instruments 1,568,380 — 1,568,380 — Cash and cash equivalents 1,434,045 1,434,045 — — Interest rate caps 415 — 415 — Counterparty collateral 186,108 — 186,108 — $ 48,854,366 $ 1,724,690 $ 47,129,676 $ — Liabilities Interest rate swap $ 789 $ — $ 789 $ — Fixed index annuities - embedded derivatives 8,790,427 — — 8,790,427 $ 8,791,216 $ — $ 789 $ 8,790,427
Schedule of Assumptions Used in Estimating Fair Value	The following table presents average lapse rate and partial withdrawal rate assumptions, by contract duration, used in estimating the fair value of the embedded derivative component of our fixed index annuity policy benefit reserves at each reporting date: Average Lapse Rates Average Partial Withdrawal Rates Contract Duration (Years) September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 1 - 5 2.05% 1.83% 3.33% 3.32% 6 - 10 7.28% 7.01% 3.33% 3.32% 11 - 15 11.35% 11.31% 3.35% 3.34% 16 - 20 11.91% 11.96% 3.21% 3.20% 20+ 11.58% 11.62% 3.21% 3.20%
Liabilities Measured at Fair Value on Recurring Basis, Level 3 Reconciliation	The following table provides a reconciliation of the beginning and ending balances for our Level 3 liabilities, which are measured at fair value on a recurring basis using significant unobservable inputs for the three and nine months ended September 30, 2018 and 2017 : Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands) Fixed index annuities - embedded derivatives Beginning balance $ 8,351,151 $ 7,552,365 $ 8,790,427 $ 6,563,288 Premiums less benefits 399,234 475,600 1,354,881 1,384,791 Change in fair value, net 196,808 41,140 (1,198,115 ) 121,026 Ending balance $ 8,947,193 $ 8,069,105 $ 8,947,193 $ 8,069,105

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2018
Investments [Abstract]
Schedule of Fixed Maturity Securities	At September 30, 2018 and December 31, 2017 , the amortized cost and fair value of fixed maturity securities were as follows: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (Dollars in thousands) September 30, 2018 Fixed maturity securities: Available for sale: United States Government full faith and credit $ 11,528 $ 79 $ (645 ) $ 10,962 United States Government sponsored agencies 1,308,358 11,824 (95,595 ) 1,224,587 United States municipalities, states and territories 3,949,293 224,586 (31,622 ) 4,142,257 Foreign government obligations 226,931 7,240 (7,671 ) 226,500 Corporate securities 28,406,182 746,913 (673,492 ) 28,479,603 Residential mortgage backed securities 1,129,176 64,183 (11,677 ) 1,181,682 Commercial mortgage backed securities 5,434,044 22,684 (119,360 ) 5,337,368 Other asset backed securities 5,222,830 35,553 (39,325 ) 5,219,058 $ 45,688,342 $ 1,113,062 $ (979,387 ) $ 45,822,017 Held for investment: Corporate security $ 77,213 $ — $ (6,100 ) $ 71,113 December 31, 2017 Fixed maturity securities: Available for sale: United States Government full faith and credit $ 11,861 $ 162 $ (147 ) $ 11,876 United States Government sponsored agencies 1,308,290 28,457 (31,730 ) 1,305,017 United States municipalities, states and territories 3,804,360 366,048 (3,596 ) 4,166,812 Foreign government obligations 228,214 13,171 (2,025 ) 239,360 Corporate securities 28,127,653 1,897,005 (145,687 ) 29,878,971 Residential mortgage backed securities 1,028,484 79,554 (2,471 ) 1,105,567 Commercial mortgage backed securities 5,531,922 82,768 (69,840 ) 5,544,850 Other asset backed securities 3,075,975 57,966 (13,405 ) 3,120,536 $ 43,116,759 $ 2,525,131 $ (268,901 ) $ 45,372,989 Held for investment: Corporate security $ 77,041 $ — $ (581 ) $ 76,460 Other investments: equity securities, available for sale: Finance, insurance, and real estate $ 292,429 $ — $ — $ 292,429
Schedule of Fixed Maturity Securities by Contractual Maturity Date	The amortized cost and fair value of fixed maturity securities at September 30, 2018 , by contractual maturity, are shown below. Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. All of our mortgage and other asset backed securities provide for periodic payments throughout their lives and are shown below as separate lines. Available for sale Held for investment Amortized Cost Fair Value Amortized Cost Fair Value (Dollars in thousands) Due in one year or less $ 283,309 $ 287,677 $ — $ — Due after one year through five years 5,564,840 5,561,473 — — Due after five years through ten years 9,893,201 9,753,983 — — Due after ten years through twenty years 9,562,224 9,883,734 — — Due after twenty years 8,598,718 8,597,042 77,213 71,113 33,902,292 34,083,909 77,213 71,113 Residential mortgage backed securities 1,129,176 1,181,682 — — Commercial mortgage backed securities 5,434,044 5,337,368 — — Other asset backed securities 5,222,830 5,219,058 — — $ 45,688,342 $ 45,822,017 $ 77,213 $ 71,113
Schedule of Components of Net Unrealized Gains on Available for Sale Fixed Maturity Securities Reported as Separate Component of Stockholders' Equity	Net unrealized gains on available for sale fixed maturity securities reported as a separate component of stockholders' equity were comprised of the following: September 30, 2018 December 31, 2017 (Dollars in thousands) Net unrealized gains on available for sale fixed maturity securities $ 133,675 $ 2,256,230 Adjustments for assumed changes in amortization of deferred policy acquisition costs and deferred sales inducements (73,225 ) (1,206,078 ) Deferred income tax valuation allowance reversal 22,534 22,534 Deferred income tax expense (a) (12,696 ) (348,087 ) Net unrealized gains reported as accumulated other comprehensive income $ 70,288 $ 724,599 (a) December 31, 2017 includes $128 million related to the impact of Tax Reform that was reclassified between accumulated other comprehensive income and retained earnings within our consolidated balance sheet during the first quarter of 2018. For more information regarding the reclassification, see Note 1 to our unaudited consolidated financial statements.
Schedule of Credit Quality of Fixed Maturity Security Portfolio by NAIC Designation	The following table summarizes the credit quality, as determined by NAIC designation, of our fixed maturity portfolio as of the dates indicated: September 30, 2018 December 31, 2017 NAIC Designation Amortized Cost Fair Value Amortized Cost Fair Value (Dollars in thousands) 1 $ 27,186,979 $ 27,478,961 $ 26,669,427 $ 28,274,379 2 16,972,448 16,868,800 15,198,551 15,869,219 3 1,406,867 1,365,147 1,161,737 1,157,420 4 180,233 156,449 134,838 117,542 5 11,200 16,898 17,015 20,927 6 7,828 6,875 12,232 9,962 $ 45,765,555 $ 45,893,130 $ 43,193,800 $ 45,449,449
Schedule of Gross Unrealized Losses on Investments, By Category and Length of Time	The following table shows our investments' gross unrealized losses and fair value, aggregated by investment category and length of time that individual securities (consisting of 2,630 and 955 securities, respectively) have been in a continuous unrealized loss position, at September 30, 2018 and December 31, 2017 : Less than 12 months 12 months or more Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses (Dollars in thousands) September 30, 2018 Fixed maturity securities: Available for sale: United States Government full faith and credit $ 3,178 $ (98 ) $ 5,989 $ (547 ) $ 9,167 $ (645 ) United States Government sponsored agencies 43,310 (2,770 ) 927,678 (92,825 ) 970,988 (95,595 ) United States municipalities, states and territories 684,699 (21,142 ) 123,625 (10,480 ) 808,324 (31,622 ) Foreign government obligations 106,283 (4,031 ) 60,641 (3,640 ) 166,924 (7,671 ) Corporate securities: Finance, insurance and real estate 2,825,957 (83,452 ) 783,568 (75,867 ) 3,609,525 (159,319 ) Manufacturing, construction and mining 2,145,542 (70,140 ) 294,755 (26,064 ) 2,440,297 (96,204 ) Utilities and related sectors 2,569,490 (87,914 ) 383,587 (34,057 ) 2,953,077 (121,971 ) Wholesale/retail trade 1,026,417 (36,525 ) 143,605 (18,263 ) 1,170,022 (54,788 ) Services, media and other 4,472,035 (135,921 ) 950,004 (105,289 ) 5,422,039 (241,210 ) Residential mortgage backed securities 396,096 (9,620 ) 41,760 (2,057 ) 437,856 (11,677 ) Commercial mortgage backed securities 2,423,197 (40,541 ) 1,610,912 (78,819 ) 4,034,109 (119,360 ) Other asset backed securities 3,066,340 (27,693 ) 191,639 (11,632 ) 3,257,979 (39,325 ) $ 19,762,544 $ (519,847 ) $ 5,517,763 $ (459,540 ) $ 25,280,307 $ (979,387 ) Held for investment: Corporate security: Insurance $ — $ — $ 71,113 $ (6,100 ) $ 71,113 $ (6,100 ) December 31, 2017 Fixed maturity securities: Available for sale: United States Government full faith and credit $ 1,565 $ (10 ) $ 6,731 $ (137 ) $ 8,296 $ (147 ) United States Government sponsored agencies 44,794 (180 ) 958,965 (31,550 ) 1,003,759 (31,730 ) United States municipalities, states and territories 44,736 (128 ) 128,499 (3,468 ) 173,235 (3,596 ) Foreign government obligations 49,663 (337 ) 12,625 (1,688 ) 62,288 (2,025 ) Corporate securities: Finance, insurance and real estate 456,244 (5,135 ) 600,655 (28,043 ) 1,056,899 (33,178 ) Manufacturing, construction and mining 222,985 (3,475 ) 231,196 (10,849 ) 454,181 (14,324 ) Utilities and related sectors 395,183 (4,099 ) 249,416 (8,901 ) 644,599 (13,000 ) Wholesale/retail trade 152,941 (1,249 ) 178,635 (11,371 ) 331,576 (12,620 ) Services, media and other 729,124 (19,000 ) 891,654 (53,565 ) 1,620,778 (72,565 ) Residential mortgage backed securities 39,771 (387 ) 32,917 (2,084 ) 72,688 (2,471 ) Commercial mortgage backed securities 1,096,757 (10,385 ) 1,306,437 (59,455 ) 2,403,194 (69,840 ) Other asset backed securities 765,531 (3,499 ) 217,595 (9,906 ) 983,126 (13,405 ) $ 3,999,294 $ (47,884 ) $ 4,815,325 $ (221,017 ) $ 8,814,619 $ (268,901 ) Held for investment: Corporate security: Insurance $ — $ — $ 76,460 $ (581 ) $ 76,460 $ (581 )
Schedule of Changes in Net Unrealized Gains/Losses on Investments	Changes in net unrealized gains on investments for the three and nine months ended September 30, 2018 and 2017 are as follows: Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands) Fixed maturity securities held for investment carried at amortized cost $ 2,947 $ (1,711 ) $ (5,519 ) $ 6,119 Investments carried at fair value: Fixed maturity securities, available for sale $ (311,954 ) $ 128,981 $ (2,122,555 ) $ 1,008,483 Equity securities, available for sale — (457 ) — (479 ) (311,954 ) 128,524 (2,122,555 ) 1,008,004 Adjustment for effect on other balance sheet accounts: Deferred policy acquisition costs and deferred sales inducements 172,566 (52,572 ) 1,132,853 (516,427 ) Deferred income tax asset/liability 29,270 (26,583 ) 207,837 (172,052 ) 201,836 (79,155 ) 1,340,690 (688,479 ) Change in net unrealized gains on investments carried at fair value $ (110,118 ) $ 49,369 $ (781,865 ) $ 319,525
Net Realized Gains (Losses) on Investments	Net realized gains (losses) on investments, excluding net OTTI losses for the three and nine months ended September 30, 2018 and 2017 , are as follows: Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands) Available for sale fixed maturity securities: Gross realized gains $ 505 $ 1,520 $ 2,845 $ 11,571 Gross realized losses (1,913 ) (1 ) (43,648 ) (4,463 ) (1,408 ) 1,519 (40,803 ) 7,108 Available for sale equity securities: Gross realized gains — 348 — 348 Other investments: Gain on sale of real estate — 12 — 56 Mortgage loans on real estate: Decrease (increase) in allowance for credit losses (1,255 ) (300 ) (785 ) 278 Recovery of specific allowance 467 — 1,189 — Gain on sale of mortgage loans — — 124 — (788 ) (300 ) 528 278 $ (2,196 ) $ 1,579 $ (40,275 ) $ 7,790
Significant Assumptions Used to Determine the Credit Loss Component of Other Than Temporary Impairment on Residential Mortgage Backed Securities	The following table presents the range of significant assumptions used to determine the credit loss component of other than temporary impairments we have recognized on residential mortgage backed securities for the nine months ended September 30, 2018 and 2017 , which are all senior level tranches within the structure of the securities: Discount Rate Default Rate Loss Severity Vintage Min Max Min Max Min Max Nine months ended September 30, 2018 Prime 2005 7.0 % 7.7 % 14 % 23 % 40 % 50 % 2007 6.6 % 6.6 % 17 % 17 % 60 % 60 % Nine months ended September 30, 2017 Prime 2005 7.0 % 7.7 % 8 % 22 % 40 % 50 % 2006 7.3 % 7.3 % 14 % 14 % 40 % 40 % 2007 6.2 % 6.6 % 15 % 19 % 50 % 60 %
Other Than Temporary Impairment by Asset Type	The following table summarizes other than temporary impairments for the three and nine months ended September 30, 2018 and 2017 , by asset type: Number of Securities Total OTTI Losses Portion of OTTI Losses Recognized in (from) Other Comprehensive Income Net OTTI Losses Recognized in Operations (Dollars in thousands) Three months ended September 30, 2018 Fixed maturity securities, available for sale: Corporate securities: Capital goods 1 $ (719 ) $ — $ (719 ) Consumer discretionary 6 (5,968 ) — (5,968 ) Energy 2 (1,212 ) — (1,212 ) Financials 5 (3,495 ) — (3,495 ) Information technology 1 (550 ) — (550 ) Telecommunications 2 (249 ) — (249 ) Transportation 1 (178 ) — (178 ) Utilities 1 (94 ) — (94 ) Commercial mortgage backed securities 1 (1,908 ) — (1,908 ) 20 $ (14,373 ) $ — $ (14,373 ) Three months ended September 30, 2017 Fixed maturity securities, available for sale: Residential mortgage backed securities 3 $ (273 ) $ (191 ) $ (464 ) Nine months ended September 30, 2018 Fixed maturity securities, available for sale: Corporate securities: Capital goods 1 $ (719 ) $ — $ (719 ) Consumer discretionary 7 (6,875 ) — (6,875 ) Energy 2 (1,212 ) — (1,212 ) Financials 5 (3,495 ) — (3,495 ) Information technology 1 (550 ) — (550 ) Telecommunications 2 (249 ) — (249 ) Transportation 1 (178 ) — (178 ) Utilities 1 (94 ) — (94 ) Residential mortgage backed securities 3 (63 ) (295 ) (358 ) Commercial mortgage backed securities 1 (1,908 ) — (1,908 ) Other asset backed securities 1 (682 ) (1,356 ) (2,038 ) 25 $ (16,025 ) $ (1,651 ) $ (17,676 ) Nine months ended September 30, 2017 Fixed maturity securities, available for sale: Residential mortgage backed securities 8 $ (273 ) $ (994 ) $ (1,267 ) Other asset backed securities 1 — (287 ) (287 ) 9 $ (273 ) $ (1,281 ) $ (1,554 )
Other Than Temporary Impairment, Credit Losses Recognized in Earnings	The cumulative portion of other than temporary impairments determined to be credit losses which have been recognized in operations for debt securities are summarized as follows: Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands) Cumulative credit loss at beginning of period $ (156,469 ) $ (153,526 ) $ (157,066 ) $ (166,375 ) Additions for the amount related to credit losses for which OTTI has not previously been recognized (14,373 ) (273 ) (16,025 ) (273 ) Additional credit losses on securities for which OTTI has previously been recognized — (191 ) (1,651 ) (1,281 ) Accumulated losses on securities that were disposed of during the period — — 3,900 13,939 Cumulative credit loss at end of period $ (170,842 ) $ (153,990 ) $ (170,842 ) $ (153,990 )
Schedule of Other Than Temporary Impairment Losses, Investments	The following table summarizes the cumulative noncredit portion of OTTI and the change in fair value since recognition of OTTI, both of which were recognized in other comprehensive income, by major type of security, for securities that are part of our investment portfolio at September 30, 2018 and December 31, 2017 : Amortized Cost OTTI Recognized in Other Comprehensive Income Change in Fair Value Since OTTI was Recognized Fair Value (Dollars in thousands) September 30, 2018 Fixed maturity securities, available for sale: Corporate securities $ 389,729 $ (3,700 ) $ 10,041 $ 396,070 Residential mortgage backed securities 255,611 (168,060 ) 202,923 290,474 Commercial mortgage backed securities 7,823 — — 7,823 Other asset backed securities 2,529 — (1,682 ) 847 $ 655,692 $ (171,760 ) $ 211,282 $ 695,214 December 31, 2017 Fixed maturity securities, available for sale: Corporate securities $ 13,015 $ (4,263 ) $ 10,739 $ 19,491 Residential mortgage backed securities 297,582 (168,355 ) 201,620 330,847 Other asset backed securities 4,567 (1,356 ) (1,875 ) 1,336 $ 315,164 $ (173,974 ) $ 210,484 $ 351,674

Mortgage Loans on Real Estate (

Mortgage Loans on Real Estate (Tables)	9 Months Ended
	Sep. 30, 2018
Mortgage Loans on Real Estate [Abstract]
Summary of Mortgage Loan Portfolio	Our mortgage loan portfolio is summarized in the following table. There were commitments outstanding of $58.5 million at September 30, 2018 . September 30, 2018 December 31, 2017 (Dollars in thousands) Principal outstanding $ 2,900,458 $ 2,674,315 Loan loss allowance (7,114 ) (7,518 ) Deferred prepayment fees (1,189 ) (1,266 ) Carrying value $ 2,892,155 $ 2,665,531
Mortgage Loan Portfolio Summarized by Geographic Region and Property Type	The mortgage loan portfolio is summarized by geographic region and property type as follows: September 30, 2018 December 31, 2017 Principal Percent Principal Percent (Dollars in thousands) Geographic distribution East $ 598,239 20.6 % $ 548,067 20.5 % Middle Atlantic 170,836 5.9 % 163,485 6.1 % Mountain 348,233 12.0 % 308,486 11.5 % New England 9,482 0.3 % 12,265 0.5 % Pacific 494,791 17.1 % 466,030 17.4 % South Atlantic 667,043 23.0 % 609,736 22.8 % West North Central 309,332 10.7 % 324,808 12.2 % West South Central 302,502 10.4 % 241,438 9.0 % $ 2,900,458 100.0 % $ 2,674,315 100.0 % Property type distribution Office $ 267,017 9.2 % $ 283,926 10.6 % Medical Office 33,950 1.2 % 34,338 1.3 % Retail 1,076,573 37.1 % 1,040,028 38.9 % Industrial/Warehouse 743,787 25.7 % 677,770 25.3 % Apartment 604,120 20.8 % 462,897 17.3 % Mixed use/other 175,011 6.0 % 175,356 6.6 % $ 2,900,458 100.0 % $ 2,674,315 100.0 %
Rollforward of Allowance for Credit Losses	The following table presents a rollforward of our specific and general valuation allowances for mortgage loans on real estate: Three Months Ended Three Months Ended Specific Allowance General Allowance Specific Allowance General Allowance (Dollars in thousands) Beginning allowance balance $ (696 ) $ (5,630 ) $ (2,049 ) $ (5,800 ) Charge-offs — — — — Recoveries 467 — — — Change in provision for credit losses (1,255 ) — — (300 ) Ending allowance balance $ (1,484 ) $ (5,630 ) $ (2,049 ) $ (6,100 ) Nine Months Ended Nine Months Ended Specific Allowance General Allowance Specific Allowance General Allowance (Dollars in thousands) Beginning allowance balance $ (1,418 ) $ (6,100 ) $ (1,327 ) $ (7,100 ) Charge-offs — — — — Recoveries 1,189 — — — Change in provision for credit losses (1,255 ) 470 (722 ) 1,000 Ending allowance balance $ (1,484 ) $ (5,630 ) $ (2,049 ) $ (6,100 )
Impaired Mortgage Loans on Real Estate by Basis of Impairment	The following table presents the total outstanding principal of loans evaluated for impairment by basis of impairment method: September 30, 2018 December 31, 2017 (Dollars in thousands) Individually evaluated for impairment $ 3,179 $ 5,445 Collectively evaluated for impairment 2,897,279 2,668,870 Total loans evaluated for impairment $ 2,900,458 $ 2,674,315
Mortgage Loans By Credit Quality Indicator	We analyze credit risk of our mortgage loans by analyzing all available evidence on loans that are delinquent and loans that are in a workout period. September 30, 2018 December 31, 2017 (Dollars in thousands) Credit Exposure - By Payment Activity Performing $ 2,898,538 $ 2,670,657 In workout — 1,436 Collateral dependent 1,920 2,222 $ 2,900,458 $ 2,674,315
Aging of Financing Receivables	Aging of financing receivables is summarized in the following table, with loans in a "workout" period as of the reporting date considered current if payments are current in accordance with agreed upon terms: 30 - 59 Days 60 - 89 Days 90 Days and Over Total Past Due Current Collateral Dependent Receivables Total Financing Receivables (Dollars in thousands) Commercial Mortgage Loans September 30, 2018 $ — $ — $ — $ — $ 2,898,538 $ 1,920 $ 2,900,458 December 31, 2017 $ — $ — $ — $ — $ 2,672,093 $ 2,222 $ 2,674,315
Impaired Financing Receivables	Financing receivables summarized in the following two tables represent all loans that we are either not currently collecting, or those we feel it is probable we will not collect all amounts due according to the contractual terms of the loan agreements (all loans that we have worked with the borrower to alleviate short-term cash flow issues, loans delinquent for 60 days or more at the reporting date, loans we have determined to be collateral dependent and loans that we have recorded specific impairments on that we feel may continue to have performance issues). Recorded Investment Unpaid Principal Balance Related Allowance (Dollars in thousands) September 30, 2018 Mortgage loans with an allowance $ 1,695 $ 3,179 $ (1,484 ) Mortgage loans with no related allowance — — — $ 1,695 $ 3,179 $ (1,484 ) December 31, 2017 Mortgage loans with an allowance $ 4,027 $ 5,445 $ (1,418 ) Mortgage loans with no related allowance 1,436 1,436 — $ 5,463 $ 6,881 $ (1,418 ) Average Recorded Investment Interest Income Recognized (Dollars in thousands) Three months ended September 30, 2018 Mortgage loans with an allowance $ 2,337 $ 37 Mortgage loans with no related allowance — — $ 2,337 $ 37 Three months ended September 30, 2017 Mortgage loans with an allowance $ 4,702 $ 21 Mortgage loans with no related allowance 1,496 22 $ 6,198 $ 43 Nine months ended September 30, 2018 Mortgage loans with an allowance $ 2,386 $ 136 Mortgage loans with no related allowance — — $ 2,386 $ 136 Nine months ended September 30, 2017 Mortgage loans with an allowance $ 5,112 $ 228 Mortgage loans with no related allowance 1,533 69 $ 6,645 $ 297
Troubled Debt Restructurings on Financing Receivables	There were no mortgage loans on commercial real estate that we determined to be a TDR at September 30, 2018. A summary of mortgage loans on commercial real estate with outstanding principal at December 31, 2017 that we determined to be TDRs are as follows: Geographic Region Number of TDRs Principal Balance Outstanding Specific Loan Loss Allowance Net Carrying Amount (Dollars in thousands) December 31, 2017 South Atlantic 1 $ 2,947 $ — $ 2,947 East 1 1,933 (467 ) 1,466 2 $ 4,880 $ (467 ) $ 4,413

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair Value of Derivative Instruments as Presented in the Consolidated Balance Sheets	The fair value of our derivative instruments, including derivative instruments embedded in fixed index annuity contracts, presented in the consolidated balance sheets are as follows: September 30, 2018 December 31, 2017 (Dollars in thousands) Assets Derivative instruments Call options $ 1,290,387 $ 1,568,380 Other assets Interest rate caps 1,244 415 Interest rate swap 1,125 — $ 1,292,756 $ 1,568,795 Liabilities Policy benefit reserves - annuity products Fixed index annuities - embedded derivatives $ 8,947,193 $ 8,790,427 Other liabilities Interest rate swap — 789 $ 8,947,193 $ 8,791,216
Schedule of Changes in Fair Value of Derivative Instruments	The changes in fair value of derivatives included in the unaudited consolidated statements of operations are as follows: Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands) Change in fair value of derivatives: Call options $ 594,872 $ 362,560 $ 273,946 $ 1,017,001 Interest rate swap 258 63 1,658 (411 ) Interest rate caps 181 (98 ) 829 (712 ) $ 595,311 $ 362,525 $ 276,433 $ 1,015,878 Change in fair value of embedded derivatives: Fixed index annuities - embedded derivatives $ 196,808 $ 41,140 $ (1,198,115 ) $ 121,026 Other changes in difference between policy benefit reserves computed using derivative accounting vs. long-duration contracts accounting 186,908 188,562 612,650 507,819 $ 383,716 $ 229,702 $ (585,465 ) $ 628,845
Schedule of Call Options by Counterparty	The notional amount and fair value of our call options by counterparty and each counterparty's current credit rating are as follows: September 30, 2018 December 31, 2017 Counterparty Credit Rating (S&P) Credit Rating (Moody's) Notional Amount Fair Value Notional Amount Fair Value (Dollars in thousands) Bank of America A+ Aa3 $ 6,215,626 $ 214,380 $ 4,645,366 $ 237,955 Barclays A A2 2,509,716 76,397 4,135,537 154,127 BNP Paribas A Aa3 — — 1,411,989 73,650 Canadian Imperial Bank of Commerce A+ Aa2 5,200,352 173,803 2,808,030 84,268 Citibank, N.A. A+ A1 4,904,171 176,825 4,104,666 219,900 Credit Suisse A A1 2,640,799 62,867 3,538,855 137,384 J.P. Morgan A+ Aa3 3,225,810 116,332 1,753,649 109,689 Morgan Stanley A+ A1 3,941,705 124,691 3,408,179 184,323 Royal Bank of Canada AA- A2 1,942,305 67,105 3,027,469 104,141 Societe Generale A A1 1,769,787 53,835 — — SunTrust A- Baa1 1,644,816 54,149 2,331,168 90,399 Wells Fargo A+ Aa2 4,659,622 163,569 4,036,255 162,781 Exchange traded 235,663 6,434 296,840 9,763 $ 38,890,372 $ 1,290,387 $ 35,498,003 $ 1,568,380
Schedule of Interest Rate Derivatives	Details regarding the interest rate swap are as follows: Notional Pay September 30, 2018 December 31, 2017 Maturity Date Amount Receive Rate Rate Counterparty Fair Value (Dollars in thousands) March 15, 2021 $ 85,500 LIBOR 2.415 % SunTrust $ 1,125 $ (789 ) Details regarding the interest rate caps are as follows: Notional Cap September 30, 2018 December 31, 2017 Maturity Date Amount Floating Rate Rate Counterparty Fair Value (Dollars in thousands) July 7, 2021 $ 40,000 LIBOR 2.50 % SunTrust $ 624 $ 207 July 8, 2021 12,000 LIBOR 2.50 % SunTrust 187 62 July 29, 2021 27,000 LIBOR 2.50 % SunTrust 433 146 $ 79,000 $ 1,244 $ 415

Notes Payable and Amounts Due_2

Notes Payable and Amounts Due Under Repurchase Agreements (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Notes Payable	Notes payable includes the following: September 30, 2018 December 31, 2017 (Dollars in thousands) Senior notes due 2027 Principal $ 500,000 $ 500,000 Unamortized debt issue costs (5,222 ) (5,572 ) Unamortized discount (314 ) (335 ) $ 494,464 $ 494,093

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the computation of earnings per common share and earnings per common share - assuming dilution: Three Months Ended Nine Months Ended 2018 2017 2018 2017 (Dollars in thousands, except share and per share data) Numerator: Net income - numerator for earnings per common share $ 169,328 $ 56,957 $ 404,193 $ 137,842 Denominator: Weighted average common shares outstanding 90,485,567 89,068,770 90,278,209 88,872,562 Effect of dilutive securities: Stock options and deferred compensation agreements 705,465 974,208 750,588 924,465 Restricted stock and restricted stock units 459,854 377,552 326,613 373,993 Denominator for earnings per common share - assuming dilution 91,650,886 90,420,530 91,355,410 90,171,020 Earnings per common share $ 1.87 $ 0.64 $ 4.48 $ 1.55 Earnings per common share - assuming dilution $ 1.85 $ 0.63 $ 4.42 $ 1.53

Significant Accounting Polici_3

Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Federal corporate tax rate, percent	21.00%	35.00%
Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New accounting pronouncement, effect of adoption, quantification	$ 128	$ 128

Fair Values of Financial Inst_3

Fair Values of Financial Instruments (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)Basis_Points	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)Basis_Points	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Level 1 to Level 2 transfers, amount	$ 0		$ 0		$ 0
Liabilities, Level 1 to Level 2 transfers, amount	0		0		0
Assets, Level 2 to Level 1 transfers, amount	0		0		0
Liabilities, Level 2 to Level 1 transfers, amount	0		0		0
Assets, transfers into Level 3, amount	0	$ 0	0	$ 0
Liabilities, transfers into Level 3, amount	0	0	0	0
Assets, transfers out of Level 3, amount	0	0	0	0
Liabilities, transfers out of Level 3, amount	0	$ 0	0	$ 0
Coinsurance ceded, fixed index annuities embedded derivatives	$ 5,017,255		$ 5,017,255		4,858,289
Fair Value, Sensitivity, Increase in Discount Rate by 10 Percent
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, sensitivity, discount rate adjustment (basis points) | Basis_Points	100		100
Fixed index annuities embedded derivative, adjustment due to change in discount rate			$ (553,900)
Deferred policy scquisition costs and deferred sales inducements, combined balance, adjustment due to change in discount rate			$ (330,200)
Fair Value, Sensitivity, Decrease in Discount Rate by 10 Percent
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, sensitivity, discount rate adjustment (basis points) | Basis_Points	100		100
Fixed index annuities embedded derivative, adjustment due to change in discount rate			$ 614,700
Deferred policy scquisition costs and deferred sales inducements, combined balance, adjustment due to change in discount rate			352,100
Fixed Index Annuities - Embedded Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Coinsurance ceded, fixed index annuities embedded derivatives	$ 592,600		$ 592,600		$ 539,700

Fair Values of Financial Inst_4

Fair Values of Financial Instruments (Fair Values and Carrying Amounts of Financial Instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Held for investment	$ 71,113	$ 76,460
Other investments	536,594	616,764
Coinsurance deposits	5,017,255	4,858,289
Liabilities
Policy benefit reserves	57,992,164	56,142,673
Interest Rate Caps
Assets
Derivative instruments	1,244	415
Carrying Amount
Assets
Available for sale securities	45,822,017	45,372,989
Held for investment	77,213	77,041
Mortgage loans on real estate	2,892,155	2,665,531
Derivative instruments	1,290,387	1,568,380
Other investments	536,594	616,764
Cash and cash equivalents	1,129,242	1,434,045
Coinsurance deposits	5,017,255	4,858,289
Counterparty collateral	179,512	186,108
Liabilities
Policy benefit reserves	57,633,261	55,786,011
Single premium immediate annuity (SPIA) benefit reserves	271,275	282,563
Notes payable	494,464	494,093
Subordinated debentures	242,875	242,565
Amounts due under repurchase agreements	116,399	0
Carrying Amount | Interest Rate Caps
Assets
Interest rate derivative assets	1,244	415
Carrying Amount | Interest Rate Swap
Assets
Interest rate derivative assets	1,125	0
Liabilities
Interest rate derivative liabilities	0	789
Fair Value
Assets
Available for sale securities	45,822,017	45,372,989
Held for investment	71,113	76,460
Mortgage loans on real estate	2,835,345	2,670,037
Derivative instruments	1,290,387	1,568,380
Other investments	528,867	605,894
Cash and cash equivalents	1,129,242	1,434,045
Coinsurance deposits	4,547,180	4,347,990
Counterparty collateral	179,512	186,108
Liabilities
Policy benefit reserves	48,792,935	46,344,931
Single premium immediate annuity (SPIA) benefit reserves	279,993	292,153
Notes payable	500,000	521,800
Subordinated debentures	238,703	244,117
Amounts due under repurchase agreements	116,399	0
Fair Value | Interest Rate Caps
Assets
Interest rate derivative assets	1,244	415
Fair Value | Interest Rate Swap
Assets
Interest rate derivative assets	1,125	0
Liabilities
Interest rate derivative liabilities	$ 0	$ 789

Fair Values of Financial Inst_5

Fair Values of Financial Instruments (Assets and Liabilities Measured on a Recurring Basis by Fair Value Hierarchy) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Interest Rate Caps
Assets
Derivative assets	$ 1,244	$ 415
Fixed Maturity Securities
Assets
Available for sale securities	45,822,017	45,372,989
Fixed Maturity Securities | United States Government Full Faith and Credit
Assets
Available for sale securities	10,962	11,876
Fixed Maturity Securities | United States Government Sponsored Agencies
Assets
Available for sale securities	1,224,587	1,305,017
Fixed Maturity Securities | United States Municipalities, States and Territories
Assets
Available for sale securities	4,142,257	4,166,812
Fixed Maturity Securities | Foreign Government Obligations
Assets
Available for sale securities	226,500	239,360
Fixed Maturity Securities | Corporate Securities
Assets
Available for sale securities	28,479,603	29,878,971
Fixed Maturity Securities | Residential Mortgage Backed Securities
Assets
Available for sale securities	1,181,682	1,105,567
Fixed Maturity Securities | Commercial Mortgage Backed Securities
Assets
Available for sale securities	5,337,368	5,544,850
Fixed Maturity Securities | Other Asset Backed Securities
Assets
Available for sale securities	5,219,058	3,120,536
Equity Securities
Assets
Available for sale securities		292,429
Fair Value, Measurements, Recurring
Assets
Derivative assets	1,290,387	1,568,380
Cash and cash equivalents	1,129,242	1,434,045
Counterparty collateral	179,512	186,108
Assets	48,630,961	48,854,366
Liabilities
Fixed index annuities - embedded derivatives	8,947,193	8,790,427
Liabilities		8,791,216
Fair Value, Measurements, Recurring | Interest Rate Caps
Assets
Interest rate derivative assets	1,244	415
Fair Value, Measurements, Recurring | Interest Rate Swap
Assets
Interest rate derivative assets	1,125
Liabilities
Interest rate derivative liabilities		789
Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Government Full Faith and Credit
Assets
Available for sale securities	10,962	11,876
Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Government Sponsored Agencies
Assets
Available for sale securities	1,224,587	1,305,017
Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Municipalities, States and Territories
Assets
Available for sale securities	4,142,257	4,166,812
Fair Value, Measurements, Recurring | Fixed Maturity Securities | Foreign Government Obligations
Assets
Available for sale securities	226,500	239,360
Fair Value, Measurements, Recurring | Fixed Maturity Securities | Corporate Securities
Assets
Available for sale securities	28,479,603	29,878,971
Fair Value, Measurements, Recurring | Fixed Maturity Securities | Residential Mortgage Backed Securities
Assets
Available for sale securities	1,181,682	1,105,567
Fair Value, Measurements, Recurring | Fixed Maturity Securities | Commercial Mortgage Backed Securities
Assets
Available for sale securities	5,337,368	5,544,850
Fair Value, Measurements, Recurring | Fixed Maturity Securities | Other Asset Backed Securities
Assets
Available for sale securities	5,219,058	3,120,536
Fair Value, Measurements, Recurring | Equity Securities
Assets
Available for sale securities	207,434	292,429
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring
Assets
Derivative assets	0	0
Cash and cash equivalents	1,129,242	1,434,045
Counterparty collateral	0	0
Assets	1,334,703	1,724,690
Liabilities
Fixed index annuities - embedded derivatives	0	0
Liabilities		0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Interest Rate Caps
Assets
Interest rate derivative assets	0	0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Interest Rate Swap
Assets
Interest rate derivative assets	0
Liabilities
Interest rate derivative liabilities		0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Government Full Faith and Credit
Assets
Available for sale securities	5,454	5,640
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Government Sponsored Agencies
Assets
Available for sale securities	0	0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Municipalities, States and Territories
Assets
Available for sale securities	0	0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Foreign Government Obligations
Assets
Available for sale securities	0	0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Corporate Securities
Assets
Available for sale securities	7	5
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Residential Mortgage Backed Securities
Assets
Available for sale securities	0	0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Commercial Mortgage Backed Securities
Assets
Available for sale securities	0	0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Other Asset Backed Securities
Assets
Available for sale securities	0	0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Equity Securities
Assets
Available for sale securities	200,000	285,000
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Assets
Derivative assets	1,290,387	1,568,380
Cash and cash equivalents	0	0
Counterparty collateral	179,512	186,108
Assets	47,296,258	47,129,676
Liabilities
Fixed index annuities - embedded derivatives	0	0
Liabilities		789
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Interest Rate Caps
Assets
Interest rate derivative assets	1,244	415
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Interest Rate Swap
Assets
Interest rate derivative assets	1,125
Liabilities
Interest rate derivative liabilities		789
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Government Full Faith and Credit
Assets
Available for sale securities	5,508	6,236
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Government Sponsored Agencies
Assets
Available for sale securities	1,224,587	1,305,017
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Municipalities, States and Territories
Assets
Available for sale securities	4,142,257	4,166,812
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Foreign Government Obligations
Assets
Available for sale securities	226,500	239,360
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Corporate Securities
Assets
Available for sale securities	28,479,596	29,878,966
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Residential Mortgage Backed Securities
Assets
Available for sale securities	1,181,682	1,105,567
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Commercial Mortgage Backed Securities
Assets
Available for sale securities	5,337,368	5,544,850
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Other Asset Backed Securities
Assets
Available for sale securities	5,219,058	3,120,536
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Equity Securities
Assets
Available for sale securities	7,434	7,429
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Assets
Derivative assets	0	0
Cash and cash equivalents	0	0
Counterparty collateral	0	0
Assets	0	0
Liabilities
Fixed index annuities - embedded derivatives	8,947,193	8,790,427
Liabilities		8,790,427
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Interest Rate Caps
Assets
Interest rate derivative assets	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Interest Rate Swap
Assets
Interest rate derivative assets	0
Liabilities
Interest rate derivative liabilities		0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Government Full Faith and Credit
Assets
Available for sale securities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Government Sponsored Agencies
Assets
Available for sale securities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | United States Municipalities, States and Territories
Assets
Available for sale securities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Foreign Government Obligations
Assets
Available for sale securities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Corporate Securities
Assets
Available for sale securities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Residential Mortgage Backed Securities
Assets
Available for sale securities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Commercial Mortgage Backed Securities
Assets
Available for sale securities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Fixed Maturity Securities | Other Asset Backed Securities
Assets
Available for sale securities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Equity Securities
Assets
Available for sale securities	$ 0	$ 0

Fair Values of Financial Inst_6

Fair Values of Financial Instruments (Assumptions Used in Estimating Fair Value) (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Expected cost of annual call options	3.10%	3.10%
Mortality rate assumption	65.00%
Fixed Index Annuity | Minimum | Contract Duration (Years), Group 1
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	1 year	1 year
Fixed Index Annuity | Minimum | Contract Duration (Years), Group 2
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	6 years	6 years
Fixed Index Annuity | Minimum | Contract Duration (Years), Group 3
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	11 years	11 years
Fixed Index Annuity | Minimum | Contract Duration (Years), Group 4
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	16 years	16 years
Fixed Index Annuity | Minimum | Contract Duration (Years), Group 5
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	20 years	20 years
Fixed Index Annuity | Maximum | Contract Duration (Years), Group 1
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	5 years	5 years
Fixed Index Annuity | Maximum | Contract Duration (Years), Group 2
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	10 years	10 years
Fixed Index Annuity | Maximum | Contract Duration (Years), Group 3
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	15 years	15 years
Fixed Index Annuity | Maximum | Contract Duration (Years), Group 4
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	20 years	20 years
Fixed Index Annuity | Average | Contract Duration (Years), Group 1
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Average lapse rates	2.05%	1.83%
Average partial withdrawal rates	3.33%	3.32%
Fixed Index Annuity | Average | Contract Duration (Years), Group 2
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Average lapse rates	7.28%	7.01%
Average partial withdrawal rates	3.33%	3.32%
Fixed Index Annuity | Average | Contract Duration (Years), Group 3
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Average lapse rates	11.35%	11.31%
Average partial withdrawal rates	3.35%	3.34%
Fixed Index Annuity | Average | Contract Duration (Years), Group 4
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Average lapse rates	11.91%	11.96%
Average partial withdrawal rates	3.21%	3.20%
Fixed Index Annuity | Average | Contract Duration (Years), Group 5
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Average lapse rates	11.58%	11.62%
Average partial withdrawal rates	3.21%	3.20%

Fair Values of Financial Inst_7

Fair Values of Financial Instruments (Reconciliation of Beginning and Ending Balances of Level 3 Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 8,351,151	$ 7,552,365	$ 8,790,427	$ 6,563,288
Premiums less benefits	399,234	475,600	1,354,881	1,384,791
Change in fair value, net	196,808	41,140	(1,198,115)	121,026
Ending balance	$ 8,947,193	$ 8,069,105	$ 8,947,193	$ 8,069,105

Investments (Narrative) (Detail

Investments (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)Securities	Sep. 30, 2017USD ($)	Dec. 31, 2017Securities
Investments [Abstract]
Percentage of fixed maturity portfolio rated investment grade based on NAIC designations	97.00%		97.00%
Number of individual securities with unrealized losses | Securities	2,630		955
Percentage of unrealized losses on fixed maturity securities where securities are rated investment grade	93.00%		83.00%
Proceeds from sales of available for sale securities	$ 1,800	$ 496.1
Scheduled principal repayments, calls and tenders for available for sale securities	$ 997.6	$ 837.7

Investments (Schedule of Amorti

Investments (Schedule of Amortized Cost and Fair Value of Fixed Maturity Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Held for investment, amortized cost	$ 77,213	$ 77,041
Held for investment	71,113	76,460
Fixed Maturity Securities
Investment Holdings [Line Items]
Available for sale, amortized cost	45,688,342	43,116,759
Available for sale, gross unrealized gains	1,113,062	2,525,131
Available for sale, gross unrealized losses	(979,387)	(268,901)
Available for sale, fair value	45,822,017	45,372,989
Fixed Maturity Securities | United States Government Full Faith and Credit
Investment Holdings [Line Items]
Available for sale, amortized cost	11,528	11,861
Available for sale, gross unrealized gains	79	162
Available for sale, gross unrealized losses	(645)	(147)
Available for sale, fair value	10,962	11,876
Fixed Maturity Securities | United States Government Sponsored Agencies
Investment Holdings [Line Items]
Available for sale, amortized cost	1,308,358	1,308,290
Available for sale, gross unrealized gains	11,824	28,457
Available for sale, gross unrealized losses	(95,595)	(31,730)
Available for sale, fair value	1,224,587	1,305,017
Fixed Maturity Securities | United States Municipalities, States and Territories
Investment Holdings [Line Items]
Available for sale, amortized cost	3,949,293	3,804,360
Available for sale, gross unrealized gains	224,586	366,048
Available for sale, gross unrealized losses	(31,622)	(3,596)
Available for sale, fair value	4,142,257	4,166,812
Fixed Maturity Securities | Foreign Government Obligations
Investment Holdings [Line Items]
Available for sale, amortized cost	226,931	228,214
Available for sale, gross unrealized gains	7,240	13,171
Available for sale, gross unrealized losses	(7,671)	(2,025)
Available for sale, fair value	226,500	239,360
Fixed Maturity Securities | Corporate Securities
Investment Holdings [Line Items]
Available for sale, amortized cost	28,406,182	28,127,653
Available for sale, gross unrealized gains	746,913	1,897,005
Available for sale, gross unrealized losses	(673,492)	(145,687)
Available for sale, fair value	28,479,603	29,878,971
Held for investment, amortized cost	77,213	77,041
Held for investment, gross unrealized gains	0	0
Held for investment, gross unrealized losses	(6,100)	(581)
Held for investment	71,113	76,460
Fixed Maturity Securities | Residential Mortgage Backed Securities
Investment Holdings [Line Items]
Available for sale, amortized cost	1,129,176	1,028,484
Available for sale, gross unrealized gains	64,183	79,554
Available for sale, gross unrealized losses	(11,677)	(2,471)
Available for sale, fair value	1,181,682	1,105,567
Fixed Maturity Securities | Commercial Mortgage Backed Securities
Investment Holdings [Line Items]
Available for sale, amortized cost	5,434,044	5,531,922
Available for sale, gross unrealized gains	22,684	82,768
Available for sale, gross unrealized losses	(119,360)	(69,840)
Available for sale, fair value	5,337,368	5,544,850
Fixed Maturity Securities | Other Asset Backed Securities
Investment Holdings [Line Items]
Available for sale, amortized cost	5,222,830	3,075,975
Available for sale, gross unrealized gains	35,553	57,966
Available for sale, gross unrealized losses	(39,325)	(13,405)
Available for sale, fair value	$ 5,219,058	3,120,536
Equity Securities
Investment Holdings [Line Items]
Available for sale, amortized cost		292,429
Available for sale, gross unrealized gains		0
Available for sale, gross unrealized losses		0
Available for sale, fair value		$ 292,429

Investments (Fixed Maturity Sec

Investments (Fixed Maturity Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Available for sale securities, due in one year or less, amortized cost	$ 283,309
Available for sale securities, due after one year through five years, amortized cost	5,564,840
Available for sale securities, due after five years through ten years, amortized cost	9,893,201
Available for sale securities, due after ten years through twenty years, amortized cost	9,562,224
Available for sale securities, due after twenty years, amortized cost	8,598,718
Available for sale securities, securities with a single maturity date, amortized cost	33,902,292
Available for sale securities, amortized cost	45,688,342	$ 43,116,759
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Available for sale securities, due in one year or less, fair value	287,677
Available for sale securities, due after one year through five years, fair value	5,561,473
Available for sale securities, due after five years through ten years, fair value	9,753,983
Available for sale securities, due after ten years through twenty years, fair value	9,883,734
Available for sale securities, due after twenty years, fair value	8,597,042
Available for sale securities, securities with a single maturity date, fair value	34,083,909
Available for sale securities, fair value	45,822,017	45,372,989
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held for investment securities, due in one year or less, amortized cost	0
Held for investment securities, due after one year through five years, amortized cost	0
Held for investment securities, due after five years through ten years, amortized cost	0
Held for investment securities, due after ten years through twenty years, amortized cost	0
Held for investment securities, due after twenty years, amortized cost	77,213
Held for investment securities, securities with a single maturity date, amortized cost	77,213
Held for investment, amortized cost	77,213	77,041
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Held for investment securities, due in one year or less, fair value	0
Held for investment securities, due after one year through five years, fair value	0
Held for investment securities, due after five years through ten years, fair value	0
Held for investment securities, due after ten years through twenty years, fair value	0
Held for investment securities, due after twenty years, fair value	71,113
Held for investment securities, securities with a single maturity date, fair value	71,113
Held for investment	71,113	$ 76,460
Residential Mortgage Backed Securities
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Available for sale securities, securities without a single maturity date, amortized cost	1,129,176
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Available for sale securities, securities without a single maturity date, fair value	1,181,682
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held for investment securities, securities without a single maturity date, amortized cost	0
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Held for investment securities, securities without a single maturity date, fair value	0
Commercial Mortgage Backed Securities
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Available for sale securities, securities without a single maturity date, amortized cost	5,434,044
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Available for sale securities, securities without a single maturity date, fair value	5,337,368
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held for investment securities, securities without a single maturity date, amortized cost	0
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Held for investment securities, securities without a single maturity date, fair value	0
Other Asset Backed Securities
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Available for sale securities, securities without a single maturity date, amortized cost	5,222,830
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Available for sale securities, securities without a single maturity date, fair value	5,219,058
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held for investment securities, securities without a single maturity date, amortized cost	0
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Held for investment securities, securities without a single maturity date, fair value	$ 0

Investments (Net Unrealized Gai

Investments (Net Unrealized Gains on Available for Sale Fixed Maturity Securities Reported as a Separate Component of Stockholders' Equity) (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Net unrealized gains on available for sale fixed maturity securities		$ 133,675	$ 2,256,230
Adjustments for assumed changes in amortization of deferred policy acquisition costs and deferred sales inducements		(73,225)	(1,206,078)
Deferred income tax valuation allowance reversal		22,534	22,534
Deferred income tax expense	[1]	(12,696)	(348,087)
Net unrealized gains reported as accumulated other comprehensive income		70,288	724,599
Accounting Standards Update 2018-02
Schedule of Available-for-sale Securities [Line Items]
New accounting pronouncement, effect of adoption, quantification		$ 128,000	$ 128,000
[1]	December 31, 2017 includes $128 million related to the impact of Tax Reform that was reclassified between accumulated other comprehensive income and retained earnings within our consolidated balance sheet during the first quarter of 2018. For more information regarding the reclassification, see Note 1 to our unaudited consolidated financial statements.

Investments (Schedule of Credit

Investments (Schedule of Credit Quality of Fixed Maturity Portfolio by NAIC Designation) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Amortized cost	$ 45,765,555	$ 43,193,800
Fair value	45,893,130	45,449,449
NAIC, Class 1 Designation
Investment Holdings [Line Items]
Amortized cost	27,186,979	26,669,427
Fair value	27,478,961	28,274,379
NAIC, Class 2 Designation
Investment Holdings [Line Items]
Amortized cost	16,972,448	15,198,551
Fair value	16,868,800	15,869,219
NAIC, Class 3 Designation
Investment Holdings [Line Items]
Amortized cost	1,406,867	1,161,737
Fair value	1,365,147	1,157,420
NAIC, Class 4 Designation
Investment Holdings [Line Items]
Amortized cost	180,233	134,838
Fair value	156,449	117,542
NAIC, Class 5 Designation
Investment Holdings [Line Items]
Amortized cost	11,200	17,015
Fair value	16,898	20,927
NAIC, Class 6 Designation
Investment Holdings [Line Items]
Amortized cost	7,828	12,232
Fair value	$ 6,875	$ 9,962

Investments (Gross Unrealized L

Investments (Gross Unrealized Losses on Investments, By Category and Length of Time) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	$ 19,762,544	$ 3,999,294
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(519,847)	(47,884)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	5,517,763	4,815,325
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(459,540)	(221,017)
Available for sale securities, continuous unrealized loss position, total, fair value	25,280,307	8,814,619
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(979,387)	(268,901)
United States Government Full Faith and Credit
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	3,178	1,565
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(98)	(10)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	5,989	6,731
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(547)	(137)
Available for sale securities, continuous unrealized loss position, total, fair value	9,167	8,296
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(645)	(147)
United States Government Sponsored Agencies
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	43,310	44,794
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(2,770)	(180)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	927,678	958,965
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(92,825)	(31,550)
Available for sale securities, continuous unrealized loss position, total, fair value	970,988	1,003,759
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(95,595)	(31,730)
United States Municipalities, States and Territories
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	684,699	44,736
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(21,142)	(128)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	123,625	128,499
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(10,480)	(3,468)
Available for sale securities, continuous unrealized loss position, total, fair value	808,324	173,235
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(31,622)	(3,596)
Foreign Government Obligations
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	106,283	49,663
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(4,031)	(337)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	60,641	12,625
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(3,640)	(1,688)
Available for sale securities, continuous unrealized loss position, total, fair value	166,924	62,288
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(7,671)	(2,025)
Corporate Securities | Finance, Insurance and Real Estate Sectors
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	2,825,957	456,244
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(83,452)	(5,135)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	783,568	600,655
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(75,867)	(28,043)
Available for sale securities, continuous unrealized loss position, total, fair value	3,609,525	1,056,899
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(159,319)	(33,178)
Corporate Securities | Manufacturing, Construction and Mining
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	2,145,542	222,985
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(70,140)	(3,475)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	294,755	231,196
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(26,064)	(10,849)
Available for sale securities, continuous unrealized loss position, total, fair value	2,440,297	454,181
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(96,204)	(14,324)
Corporate Securities | Utilities and Related Sectors
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	2,569,490	395,183
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(87,914)	(4,099)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	383,587	249,416
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(34,057)	(8,901)
Available for sale securities, continuous unrealized loss position, total, fair value	2,953,077	644,599
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(121,971)	(13,000)
Corporate Securities | Wholesale/Retail Trade
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	1,026,417	152,941
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(36,525)	(1,249)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	143,605	178,635
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(18,263)	(11,371)
Available for sale securities, continuous unrealized loss position, total, fair value	1,170,022	331,576
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(54,788)	(12,620)
Corporate Securities | Services, Media and Other
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	4,472,035	729,124
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(135,921)	(19,000)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	950,004	891,654
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(105,289)	(53,565)
Available for sale securities, continuous unrealized loss position, total, fair value	5,422,039	1,620,778
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(241,210)	(72,565)
Corporate Securities | Insurance
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Held for investment securities, continuous unrealized loss position, less than 12 months, fair value	0	0
Held for investment securities, continuous unrealized loss position, less than 12 months, unrealized losses	0	0
Held for investment securities, continuous unrealized loss position, 12 months or longer, fair value	71,113	76,460
Held for investment securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(6,100)	(581)
Held for investment securities, continuous unrealized loss position, total, fair value	71,113	76,460
Held for investment securities, continuous unrealized loss position, total, unrealized losses	(6,100)	(581)
Residential Mortgage Backed Securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	396,096	39,771
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(9,620)	(387)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	41,760	32,917
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(2,057)	(2,084)
Available for sale securities, continuous unrealized loss position, total, fair value	437,856	72,688
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(11,677)	(2,471)
Commercial Mortgage Backed Securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	2,423,197	1,096,757
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(40,541)	(10,385)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	1,610,912	1,306,437
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(78,819)	(59,455)
Available for sale securities, continuous unrealized loss position, total, fair value	4,034,109	2,403,194
Available for sale securities, continuous unrealized loss position, total, unrealized losses	(119,360)	(69,840)
Other Asset Backed Securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale securities, continuous unrealized loss position, less than 12 months, fair value	3,066,340	765,531
Available for sale securities, continuous unrealized loss position, less than 12 months, unrealized losses	(27,693)	(3,499)
Available for sale securities, continuous unrealized loss position, 12 months or longer, fair value	191,639	217,595
Available for sale securities, continuous unrealized loss position, 12 months or longer, unrealized losses	(11,632)	(9,906)
Available for sale securities, continuous unrealized loss position, total, fair value	3,257,979	983,126
Available for sale securities, continuous unrealized loss position, total, unrealized losses	$ (39,325)	$ (13,405)

Investments (Changes in Net Unr

Investments (Changes in Net Unrealized Gains on Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investment Holdings [Line Items]
Fixed maturity securities held for investment carried at amortized cost	$ 2,947	$ (1,711)	$ (5,519)	$ 6,119
Investments carried at fair value, available for sale	(311,954)	128,524	(2,122,555)	1,008,004
Adjustment for effect on other balance sheet accounts:
Deferred policy acquisition costs and deferred sales inducements	172,566	(52,572)	1,132,853	(516,427)
Deferred income tax asset/liability	29,270	(26,583)	207,837	(172,052)
Total adjustment for effect on other balance sheet accounts	201,836	(79,155)	1,340,690	(688,479)
Change in net unrealized gains on investments carried at fair value	(110,118)	49,369	(781,865)	319,525
Fixed Maturity Securities
Investment Holdings [Line Items]
Investments carried at fair value, available for sale	(311,954)	128,981	(2,122,555)	1,008,483
Equity Securities
Investment Holdings [Line Items]
Investments carried at fair value, available for sale	$ 0	$ (457)	$ 0	$ (479)

Investments (Net Realized Gains

Investments (Net Realized Gains (Losses) on Invesments, Excluding Other Than Temporary Impairments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Gain (Loss) on Investments [Line Items]
Net realized gains (losses) on investments, excluding other than temporary impairment (OTTI) losses	$ (2,196)	$ 1,579	$ (40,275)	$ 7,790
Fixed Maturity Securities
Gain (Loss) on Investments [Line Items]
Gross realized gains	505	1,520	2,845	11,571
Gross realized losses	(1,913)	(1)	(43,648)	(4,463)
Gross realized gains (losses), excluding other than temporary impairments	(1,408)	1,519	(40,803)	7,108
Equity Securities
Gain (Loss) on Investments [Line Items]
Gross realized gains	0	348	0	348
Other Investments
Gain (Loss) on Investments [Line Items]
Gain on sale of real estate	0	12	0	56
Mortgage Loans on Real Estate
Gain (Loss) on Investments [Line Items]
Decrease (increase) in allowance for credit losses	(1,255)	(300)	(785)	278
Recovery of specific allowance	467	0	1,189	0
Gain on sale of mortgage loans	0	0	124	0
Change in allowance for credit losses and recoveries	$ (788)	$ (300)	$ 528	$ 278

Investments (Significant Assump

Investments (Significant Assumptions in Determining Credit Loss Component of Other Than Temporary Impairment on Residential Mortgage Backed Securities) (Details) - Residential Mortgage Backed Securities - Prime Sector	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Vintage Year 2005 | Minimum
Schedule of Available-for-sale Securities [Line Items]
Discount rate	7.00%	7.00%
Default rate	14.00%	8.00%
Loss severity	40.00%	40.00%
Vintage Year 2005 | Maximum
Schedule of Available-for-sale Securities [Line Items]
Discount rate	7.70%	7.70%
Default rate	23.00%	22.00%
Loss severity	50.00%	50.00%
Vintage Year 2006 | Minimum
Schedule of Available-for-sale Securities [Line Items]
Discount rate		7.30%
Default rate		14.00%
Loss severity		40.00%
Vintage Year 2006 | Maximum
Schedule of Available-for-sale Securities [Line Items]
Discount rate		7.30%
Default rate		14.00%
Loss severity		40.00%
Vintage Year 2007 | Minimum
Schedule of Available-for-sale Securities [Line Items]
Discount rate	6.60%	6.20%
Default rate	17.00%	15.00%
Loss severity	60.00%	50.00%
Vintage Year 2007 | Maximum
Schedule of Available-for-sale Securities [Line Items]
Discount rate	6.60%	6.60%
Default rate	17.00%	19.00%
Loss severity	60.00%	60.00%

Investments (Other Than Tempora

Investments (Other Than Temporary Impairments by Asset Type) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)Securities	Sep. 30, 2017USD ($)Securities	Sep. 30, 2018USD ($)Securities	Sep. 30, 2017USD ($)Securities
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities	20		25	9
Total OTTI losses	$ (14,373)	$ (273)	$ (16,025)	$ (273)
Portion of OTTI losses recognized in (from) other comprehensive income	0	(191)	(1,651)	(1,281)
Net OTTI losses recognized in operations	$ (14,373)	$ (464)	$ (17,676)	$ (1,554)
Corporate Securities | Capital Goods
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities	1		1
Total OTTI losses	$ (719)		$ (719)
Portion of OTTI losses recognized in (from) other comprehensive income	0		0
Net OTTI losses recognized in operations	$ (719)		$ (719)
Corporate Securities | Consumer Discretionary
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities	6		7
Total OTTI losses	$ (5,968)		$ (6,875)
Portion of OTTI losses recognized in (from) other comprehensive income	0		0
Net OTTI losses recognized in operations	$ (5,968)		$ (6,875)
Corporate Securities | Energy
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities	2		2
Total OTTI losses	$ (1,212)		$ (1,212)
Portion of OTTI losses recognized in (from) other comprehensive income	0		0
Net OTTI losses recognized in operations	$ (1,212)		$ (1,212)
Corporate Securities | Financials
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities	5		5
Total OTTI losses	$ (3,495)		$ (3,495)
Portion of OTTI losses recognized in (from) other comprehensive income	0		0
Net OTTI losses recognized in operations	$ (3,495)		$ (3,495)
Corporate Securities | Information Technology
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities	1		1
Total OTTI losses	$ (550)		$ (550)
Portion of OTTI losses recognized in (from) other comprehensive income	0		0
Net OTTI losses recognized in operations	$ (550)		$ (550)
Corporate Securities | Telecommunications
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities	2		2
Total OTTI losses	$ (249)		$ (249)
Portion of OTTI losses recognized in (from) other comprehensive income	0		0
Net OTTI losses recognized in operations	$ (249)		$ (249)
Corporate Securities | Transportation
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities	1		1
Total OTTI losses	$ (178)		$ (178)
Portion of OTTI losses recognized in (from) other comprehensive income	0		0
Net OTTI losses recognized in operations	$ (178)		$ (178)
Corporate Securities | Utilities
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities	1		1
Total OTTI losses	$ (94)		$ (94)
Portion of OTTI losses recognized in (from) other comprehensive income	0		0
Net OTTI losses recognized in operations	$ (94)		$ (94)
Residential Mortgage Backed Securities
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities		3	3	8
Total OTTI losses		$ (273)	$ (63)	$ (273)
Portion of OTTI losses recognized in (from) other comprehensive income		(191)	(295)	(994)
Net OTTI losses recognized in operations		$ (464)	$ (358)	$ (1,267)
Commercial Mortgage Backed Securities
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities	1		1
Total OTTI losses	$ (1,908)		$ (1,908)
Portion of OTTI losses recognized in (from) other comprehensive income	0		0
Net OTTI losses recognized in operations	$ (1,908)		$ (1,908)
Other Asset Backed Securities
Other than Temporary Impairment Losses, Investments [Abstract]
Other than temporary impairment, number of securities | Securities			1	1
Total OTTI losses			$ (682)	$ 0
Portion of OTTI losses recognized in (from) other comprehensive income			(1,356)	(287)
Net OTTI losses recognized in operations			$ (2,038)	$ (287)

Investments (Cumulative Credit

Investments (Cumulative Credit Loss Portion of Other Than Temporary Impairment Recognized in Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investments [Abstract]
Cumulative credit loss at beginning of period	$ (156,469)	$ (153,526)	$ (157,066)	$ (166,375)
Additions for the amount related to credit losses for which OTTI has not previously been recognized	(14,373)	(273)	(16,025)	(273)
Additional credit losses on securities for which OTTI has previously been recognized	0	(191)	(1,651)	(1,281)
Accumulated losses on securities that were disposed of during the period	0	0	3,900	13,939
Cumulative credit loss at end of period	$ (170,842)	$ (153,990)	$ (170,842)	$ (153,990)

Investments (Cumulative Noncred

Investments (Cumulative Noncredit Portion of Other Than Temporary Impairment Recognized in Other Comprehensive Income and Change in Fair Value Since Other Than Temporary Impairment) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Amortized cost	$ 655,692	$ 315,164
OTTI recognized in other comprehensive income	(171,760)	(173,974)
Change in fair value since OTTI was recognized	211,282	210,484
Fair value	695,214	351,674
Corporate Securities
Investment Holdings [Line Items]
Amortized cost	389,729	13,015
OTTI recognized in other comprehensive income	(3,700)	(4,263)
Change in fair value since OTTI was recognized	10,041	10,739
Fair value	396,070	19,491
Residential Mortgage Backed Securities
Investment Holdings [Line Items]
Amortized cost	255,611	297,582
OTTI recognized in other comprehensive income	(168,060)	(168,355)
Change in fair value since OTTI was recognized	202,923	201,620
Fair value	290,474	330,847
Commercial Mortgage Backed Securities
Investment Holdings [Line Items]
Amortized cost	7,823
OTTI recognized in other comprehensive income	0
Change in fair value since OTTI was recognized	0
Fair value	7,823
Other Asset Backed Securities
Investment Holdings [Line Items]
Amortized cost	2,529	4,567
OTTI recognized in other comprehensive income	0	(1,356)
Change in fair value since OTTI was recognized	(1,682)	(1,875)
Fair value	$ 847	$ 1,336

Mortgage Loans on Real Estate_2

Mortgage Loans on Real Estate (Narrative) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)portfolio_segment	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)
Mortgage Loans on Real Estate [Abstract]
Number of portfolio segments that make up financing receivables | portfolio_segment	1
Real estate owned	$ 0		$ 0
Impaired mortgage loans, workout terms, interest only payments, six month terms	6 months
Impaired mortgage loans, workout terms, interest only payments, twelve month terms	12 months
Impaired mortgage loans, workout terms, cash flow sweep, number of months	12 months
Number of days past due, non-accrual status	90 days
Outstanding principal of loans in a non-accrual status	$ 1,900	$ 2,200
Minimum
Mortgage Loans on Real Estate [Line Items]
Number of days past due, delinquent status	60 days
Commercial Real Estate Portfolio Segment
Mortgage Loans on Real Estate [Line Items]
Commitments outstanding	$ 58,500

Mortgage Loans on Real Estate_3

Mortgage Loans on Real Estate (Summary of Mortgage Loan Portfolio) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Mortgage Loans on Real Estate [Abstract]
Principal outstanding	$ 2,900,458	$ 2,674,315
Loan loss allowance	(7,114)	(7,518)
Deferred prepayment fees	(1,189)	(1,266)
Mortgage loans on real estate	$ 2,892,155	$ 2,665,531

Mortgage Loans on Real Estate_4

Mortgage Loans on Real Estate (Mortgage Loan Portfolio Summarized by Geographic Region and Property Type) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 2,900,458	$ 2,674,315
Percent	100.00%	100.00%
East
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 598,239	$ 548,067
Percent	20.60%	20.50%
Middle Atlantic
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 170,836	$ 163,485
Percent	5.90%	6.10%
Mountain
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 348,233	$ 308,486
Percent	12.00%	11.50%
New England
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 9,482	$ 12,265
Percent	0.30%	0.50%
Pacific
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 494,791	$ 466,030
Percent	17.10%	17.40%
South Atlantic
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 667,043	$ 609,736
Percent	23.00%	22.80%
West North Central
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 309,332	$ 324,808
Percent	10.70%	12.20%
West South Central
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 302,502	$ 241,438
Percent	10.40%	9.00%
Office
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 267,017	$ 283,926
Percent	9.20%	10.60%
Medical Office
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 33,950	$ 34,338
Percent	1.20%	1.30%
Retail
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 1,076,573	$ 1,040,028
Percent	37.10%	38.90%
Industrial/Warehouse
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 743,787	$ 677,770
Percent	25.70%	25.30%
Apartment
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 604,120	$ 462,897
Percent	20.80%	17.30%
Mixed Use/Other
Mortgage Loans on Real Estate [Line Items]
Principal outstanding	$ 175,011	$ 175,356
Percent	6.00%	6.60%

Mortgage Loans on Real Estate_5

Mortgage Loans on Real Estate (Allowance for Loan Losses Rollforward) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning allowance balance			$ (7,518)
Ending allowance balance	$ (7,114)		(7,114)
Specific Allowance
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning allowance balance	(696)	$ (2,049)	(1,418)	$ (1,327)
Charge-offs	0	0	0	0
Recoveries	467	0	1,189	0
Change in provision for credit losses	(1,255)	0	(1,255)	(722)
Ending allowance balance	(1,484)	(2,049)	(1,484)	(2,049)
General Allowance
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning allowance balance	(5,630)	(5,800)	(6,100)	(7,100)
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Change in provision for credit losses	0	(300)	470	1,000
Ending allowance balance	$ (5,630)	$ (6,100)	$ (5,630)	$ (6,100)

Mortgage Loans on Real Estate_6

Mortgage Loans on Real Estate (Impaired Mortgage Loans on Real Estate by Basis of Impairment) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Mortgage Loans on Real Estate [Abstract]
Individually evaluated for impairment	$ 3,179	$ 5,445
Collectively evaluated for impairment	2,897,279	2,668,870
Principal outstanding	$ 2,900,458	$ 2,674,315

Mortgage Loans on Real Estate_7

Mortgage Loans on Real Estate (Mortgage Loans by Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Mortgage Loans on Real Estate [Abstract]
Performing	$ 2,898,538	$ 2,670,657
In workout	0	1,436
Collateral dependent	1,920	2,222
Principal outstanding	$ 2,900,458	$ 2,674,315

Mortgage Loans on Real Estate_8

Mortgage Loans on Real Estate (Schedule of Financing Receivables Past Due) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial mortgage loans, past due	$ 0	$ 0
Commercial mortgage loans, current	2,898,538	2,672,093
Commercial mortgage loans, collateral dependent receivables	1,920	2,222
Principal outstanding	2,900,458	2,674,315
30 to 59 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial mortgage loans, past due	0	0
60 to 89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial mortgage loans, past due	0	0
90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial mortgage loans, past due	$ 0	$ 0

Mortgage Loans on Real Estate_9

Mortgage Loans on Real Estate (Schedule of Impaired Financing Receivables) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Mortgage loans with an allowance, recorded investment	$ 1,695		$ 1,695		$ 4,027
Mortgage loans with no related allowance, recorded investment	0		0		1,436
Impaired mortgage loans, recorded investment	1,695		1,695		5,463
Mortgage loans with an allowance, unpaid principal balance	3,179		3,179		5,445
Mortgage loans with no related allowance, unpaid principal balance	0		0		1,436
Impaired mortgage loans, unpaid principal balance	3,179		3,179		6,881
Mortgage loans with an allowance, related allowance	(1,484)		(1,484)		$ (1,418)
Mortgage loans with an allowance, average recorded investment	2,337	$ 4,702	2,386	$ 5,112
Mortgage loans with no related allowance, average recorded investment	0	1,496	0	1,533
Impaired mortgage loans, average recorded investment	2,337	6,198	2,386	6,645
Mortgage loans with an allowance, interest income recognized	37	21	136	228
Mortgage loans with no related allowance, interest income recognized	0	22	0	69
Impaired mortgage loans, interest income reoognized	$ 37	$ 43	$ 136	$ 297

Mortgage Loans on Real Estat_10

Mortgage Loans on Real Estate (Troubled Debt Restructurings) (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018loans	Dec. 31, 2017USD ($)loans
Financing Receivable, Modifications [Line Items]
Number of TDRs | loans	0	2
Principal balance outstanding		$ 4,880
Specific loan loss allowance		(467)
Net carrying amount		$ 4,413
South Atlantic
Financing Receivable, Modifications [Line Items]
Number of TDRs | loans		1
Principal balance outstanding		$ 2,947
Specific loan loss allowance		0
Net carrying amount		$ 2,947
East
Financing Receivable, Modifications [Line Items]
Number of TDRs | loans		1
Principal balance outstanding		$ 1,933
Specific loan loss allowance		(467)
Net carrying amount		$ 1,466

Derivative Instruments (Narrati

Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative collateral	$ 1,300	$ 1,600
Credit risk, maximum exposure	$ 18.8	$ 11.9
Call Options
Derivative [Line Items]
Derivative, term of contract	1 year
Interest Rate Swap
Derivative [Line Items]
Derivative, term of contract	7 years
Interest Rate Caps
Derivative [Line Items]
Derivative, term of contract	7 years
Interest Rate Caps | London Interbank Offered Rate (LIBOR)
Derivative [Line Items]
Derivative, cap interest rate	2.50%

Derivative Instruments (Fair Va

Derivative Instruments (Fair Value of Derivative Instruments as Presented in the Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative assets	$ 1,290,387	$ 1,568,380
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative assets	1,292,756	1,568,795
Derivative liabilities	8,947,193	8,791,216
Call Options | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative assets	1,290,387	1,568,380
Interest Rate Caps | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative assets	1,244	415
Interest Rate Swap | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative assets	1,125	0
Derivative liabilities	0	789
Fixed Index Annuities - Embedded Derivatives | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ 8,947,193	$ 8,790,427

Derivative Instruments (Change

Derivative Instruments (Change in Fair Value of Derivatives Included in the Consolidated Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivatives	$ 595,311	$ 362,525	$ 276,433	$ 1,015,878
Change in fair value of embedded derivatives	383,716	229,702	(585,465)	628,845
Call Options
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivatives	594,872	362,560	273,946	1,017,001
Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivatives	258	63	1,658	(411)
Interest Rate Caps
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivatives	181	(98)	829	(712)
Fixed Index Annuities - Embedded Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of embedded derivatives	196,808	41,140	(1,198,115)	121,026
Other Changes in Difference Between Policy Benefit Reserves Computed Using Derivative Accounting Vs. Long-Duration Contracts Accounting
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of embedded derivatives	$ 186,908	$ 188,562	$ 612,650	$ 507,819

Derivative Instruments (Derivat

Derivative Instruments (Derivative Call Options, Notional Amount and Fair Value, by Counterparty) (Details) - Call Options - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Notional amount	$ 38,890,372	$ 35,498,003
Derivative instruments	1,290,387	1,568,380
Bank of America
Derivative [Line Items]
Notional amount	6,215,626	4,645,366
Derivative instruments	214,380	237,955
Barclays
Derivative [Line Items]
Notional amount	2,509,716	4,135,537
Derivative instruments	76,397	154,127
BNP Paribas
Derivative [Line Items]
Notional amount	0	1,411,989
Derivative instruments	0	73,650
Canadian Imperial Bank of Commerce
Derivative [Line Items]
Notional amount	5,200,352	2,808,030
Derivative instruments	173,803	84,268
Citibank, N.A.
Derivative [Line Items]
Notional amount	4,904,171	4,104,666
Derivative instruments	176,825	219,900
Credit Suisse
Derivative [Line Items]
Notional amount	2,640,799	3,538,855
Derivative instruments	62,867	137,384
J.P. Morgan
Derivative [Line Items]
Notional amount	3,225,810	1,753,649
Derivative instruments	116,332	109,689
Morgan Stanley
Derivative [Line Items]
Notional amount	3,941,705	3,408,179
Derivative instruments	124,691	184,323
Royal Bank of Canada
Derivative [Line Items]
Notional amount	1,942,305	3,027,469
Derivative instruments	67,105	104,141
Societe Generale
Derivative [Line Items]
Notional amount	1,769,787	0
Derivative instruments	53,835	0
SunTrust
Derivative [Line Items]
Notional amount	1,644,816	2,331,168
Derivative instruments	54,149	90,399
Wells Fargo
Derivative [Line Items]
Notional amount	4,659,622	4,036,255
Derivative instruments	163,569	162,781
Exchange Traded
Derivative [Line Items]
Notional amount	235,663	296,840
Derivative instruments	$ 6,434	$ 9,763

Derivative Instruments (Interes

Derivative Instruments (Interest Rate Swap) (Details) - Interest Rate Swap, Maturity Date, March 15, 2021, 2.415% - Interest Rate Swap - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Notional amount	$ 85,500
Pay rate	2.415%
Derivative assets	$ 1,125
Derivative liabilities		$ (789)

Derivative Instruments (Inter_2

Derivative Instruments (Interest Rate Caps) (Details) - Interest Rate Caps - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Notional amount	$ 79,000
Derivative assets	1,244	$ 415
Interest Rate Caps, Maturity Date, July 7, 2021, 2.50%
Derivative [Line Items]
Notional amount	$ 40,000
Cap rate	2.50%
Derivative assets	$ 624	207
Interest Rate Caps, Maturity Date, July 8, 2021, 2.50%
Derivative [Line Items]
Notional amount	$ 12,000
Cap rate	2.50%
Derivative assets	$ 187	62
Interest Rate Caps, Maturity Date, July 29, 2021, 2.50%
Derivative [Line Items]
Notional amount	$ 27,000
Cap rate	2.50%
Derivative assets	$ 433	$ 146

Notes Payable and Amounts Due_3

Notes Payable and Amounts Due Under Repurchase Agreements (Schedule of Notes Payable) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Jun. 16, 2017
Debt Instrument [Line Items]
Notes payable	$ 494,464	$ 494,093
June 2027 Notes
Debt Instrument [Line Items]
Debt instrument, face amount	500,000	500,000	$ 500,000
Unamortized debt issue costs	(5,222)	(5,572)
Unamortized discount	$ (314)	$ (335)	$ (300)

Notes Payable and Amounts Due_4

Notes Payable and Amounts Due Under Repurchase Agreements (2027 Notes Narrative) (Details) - June 2027 Notes - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Jun. 16, 2017
Debt Instrument [Line Items]
Debt instrument, face amount	$ 500,000	$ 500,000	$ 500,000
Interest rate			5.00%
Unamortized discount	$ 314	$ 335	$ 300
Debt financing costs			$ 5,800

Notes Payable and Amounts Due_5

Notes Payable and Amounts Due Under Repurchase Agreements (Repurchase Agreements Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Debt Disclosure [Abstract]
Repurchase agreement, average borrowings	$ 5.1	$ 22.4	$ 41.4	$ 53.3
Repurchase agreement, maximum amount borrowed			$ 544.1	$ 274.5
Repurchase agreement, weighted average interest rate	0.00%	1.35%	1.66%	0.83%

Commitments and Contingencies (

Commitments and Contingencies (Narrative) (Details) $ in Millions	Sep. 30, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Unfunded commitments to limited partnerships	$ 47.3
Unfunded commitments to privately placed corporate securities	$ 60

Earnings Per Share (Schedule of

Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share, Basic and Diluted [Line Items]
Net income - numerator for earnings per common share	$ 169,328	$ 56,957	$ 404,193	$ 137,842
Weighted average common shares outstanding (shares)	90,485,567	89,068,770	90,278,209	88,872,562
Denominator for earnings per common share - assuming dilution (shares)	91,650,886	90,420,530	91,355,410	90,171,020
Earnings per common share	$ 1.87	$ 0.64	$ 4.48	$ 1.55
Earnings per common share - assuming dilution	$ 1.85	$ 0.63	$ 4.42	$ 1.53
Stock Options and Deferred Compensation Agreements
Earnings Per Share, Basic and Diluted [Line Items]
Effect of dilutive securities: share-based payment arrangements (shares)	705,465	974,208	750,588	924,465
Restricted Stock and Restricted Stock Units
Earnings Per Share, Basic and Diluted [Line Items]
Effect of dilutive securities: share-based payment arrangements (shares)	459,854	377,552	326,613	373,993
Stock Options
Earnings Per Share, Basic and Diluted [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (shares)	0	0	0	0