Fair Value of Assets and Liabilities (Changes in Level 3 Assets and Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Equity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	$ 5,616	$ 10,617	$ 5,705	$ 9,758
Purchases	0	0	0	0
Sales	(734)	(1,008)	(929)	(1,008)
Issuances	0	0	0	0
Settlements	0	0	0	0
Other	0	0	0	147
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Fair Value, end of period	5,363	9,309	5,363	9,309
Total gains (losses) (realized/unrealized):
Included in earnings	481	(300)	587	412
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	480	(462)	598	250
Equity Securities | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	0	0	0
Equity Securities | Other income
Total gains (losses) (realized/unrealized):
Included in earnings	481	(300)	587	412
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	480	(462)	598	250
Equity Securities | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Equity Securities | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Other invested assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period		0		147
Purchases		0		0
Sales		0		0
Issuances		0		0
Settlements		0		0
Other		0		(147)
Transfers into Level 3		0		0
Transfers out of Level 3		0		0
Fair Value, end of period		0		0
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		0		0
Other invested assets | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		0		0
Other invested assets | Other income
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		0		0
Other invested assets | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Other invested assets | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Short-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period		11		87
Purchases		0		0
Sales		0		0
Issuances		0		0
Settlements		(9)		(31)
Other		0		(1)
Transfers into Level 3		0		0
Transfers out of Level 3		0		0
Fair Value, end of period		0		0
Total gains (losses) (realized/unrealized):
Included in earnings		(2)		(55)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		(2)		(55)
Short-term investments | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings		(2)		(55)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		(2)		(55)
Short-term investments | Other income
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		0		0
Short-term investments | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Short-term investments | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Reinsurance recoverables
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	283,991	195,497	239,911	244,006
Purchases	4,518	4,662	9,077	9,513
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	0	0	0	0
Other	(1)	795	21,895	(11,523)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Fair Value, end of period	339,744	185,258	339,744	185,258
Total gains (losses) (realized/unrealized):
Included in earnings	51,236	(15,696)	68,861	(56,738)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	53,335	(14,217)	72,829	(52,511)
Reinsurance recoverables | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	51,236	(15,696)	68,861	(56,738)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	53,335	(14,217)	72,829	(52,511)
Reinsurance recoverables | Other income
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	0	0	0
Reinsurance recoverables | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Reinsurance recoverables | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Receivables from parents and affiliates
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period		34,163		0
Purchases		0		0
Sales		0		0
Issuances		0		0
Settlements		0		0
Other		0		0
Transfers into Level 3		0		34,269
Transfers out of Level 3		(34,163)		(34,163)
Fair Value, end of period		0		0
Total gains (losses) (realized/unrealized):
Included in earnings		0		(106)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		0		0
Receivables from parents and affiliates | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		0		0
Receivables from parents and affiliates | Other income
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		0		0
Receivables from parents and affiliates | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings		0		(106)
Receivables from parents and affiliates | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Future policy benefits
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	(9,316,905)	(6,578,210)	(8,332,474)	(8,151,902)
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	(264,465)	(256,229)	(521,806)	(511,149)
Settlements	0	0	0	0
Other	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Fair Value, end of period	(11,738,480)	(6,222,612)	(11,738,480)	(6,222,612)
Total gains (losses) (realized/unrealized):
Included in earnings	(2,157,110)	611,827	(2,884,200)	2,440,439
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(2,240,816)	537,900	(3,025,994)	2,272,290
Future policy benefits | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	(2,157,110)	611,827	(2,884,200)	2,440,439
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(2,240,816)	537,900	(3,025,994)	2,272,290
Future policy benefits | Other income
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	0	0	0
Future policy benefits | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Future policy benefits | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Policyholders' account balances
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	(80,579)	0	(42,350)	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	(35,428)	(13,790)	(65,674)	(13,790)
Settlements	0	0	0	0
Other	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Fair Value, end of period	(121,102)	(13,835)	(121,102)	(13,835)
Total gains (losses) (realized/unrealized):
Included in earnings	(5,095)	(45)	(13,078)	(45)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(3,299)	(45)	(11,282)	(45)
Policyholders' account balances | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	(5,095)	(45)	(13,078)	(45)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(3,299)	(45)	(11,282)	(45)
Policyholders' account balances | Other income
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	0	0	0
Policyholders' account balances | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Policyholders' account balances | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Reinsurance payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period		(129)
Purchases		0
Sales		0
Issuances		0
Settlements		0
Other		129
Transfers into Level 3		0
Transfers out of Level 3		0
Fair Value, end of period		0		0
Total gains (losses) (realized/unrealized):
Included in earnings		0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		0
Reinsurance payable | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		0		0
Reinsurance payable | Other income
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings		0		0
Reinsurance payable | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Reinsurance payable | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings		0		0
Available-for-sale | Fixed maturities | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	(1,175)	(119)	(1,900)	(185)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	(144)	(1,998)	(221)
Available-for-sale | Fixed maturities | Other income
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	0	0	0
Available-for-sale | Fixed maturities | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	1,473	(3,002)	2,914	(1,952)
Available-for-sale | Fixed maturities | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	99	52	138	147
Available-for-sale | Fixed maturities | U.S. government
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	8,779	5,882	8,132	5,237
Purchases	601	776	1,248	1,421
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	0	0	0	0
Other	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Fair Value, end of period	9,380	6,658	9,380	6,658
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	0	0	0
Available-for-sale | Fixed maturities | Corporate securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	84,800	90,273	85,452	95,206
Purchases	4,087	4,874	7,313	5,025
Sales	0	(205)	0	(241)
Issuances	0	0	0	0
Settlements	(16,626)	(2,369)	(22,089)	(8,404)
Other	0	0	0	23
Transfers into Level 3	815	6,941	1,790	6,941
Transfers out of Level 3	(2,018)	0	(2,018)	(215)
Fair Value, end of period	71,071	96,849	71,071	96,849
Total gains (losses) (realized/unrealized):
Included in earnings	13	(2,665)	623	(1,486)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	(144)	(1,996)	(221)
Available-for-sale | Fixed maturities | Structured securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	50,258	256,244	9,336	185,358
Purchases	0	21,000	44,273	84,810
Sales	0	(193)	0	(193)
Issuances	0	0	0	0
Settlements	(339)	(14,714)	(4,386)	(23,613)
Other	0	0	0	0
Transfers into Level 3	0	10,025	551	51,979
Transfers out of Level 3	(30,578)	(212,780)	(30,578)	238,659
Fair Value, end of period	19,725	59,178	19,725	59,178
Total gains (losses) (realized/unrealized):
Included in earnings	384	(404)	529	(504)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	$ 0	(2)	$ 0
Trading | Fixed maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	0		0
Purchases	0		0
Sales	0		0
Issuances	0		0
Settlements	0		0
Other	0		0
Transfers into Level 3	5,021		5,021
Transfers out of Level 3	0		0
Fair Value, end of period	4,044		4,044
Total gains (losses) (realized/unrealized):
Included in earnings	(977)		(977)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(972)		(972)
Trading | Fixed maturities | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	0		0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0		0
Trading | Fixed maturities | Other income
Total gains (losses) (realized/unrealized):
Included in earnings	(972)		(972)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(972)		(972)
Trading | Fixed maturities | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	0		0
Trading | Fixed maturities | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	$ (5)		$ (5)