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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	$ 9,196	$ 15,991	$ 9,898	$ 15,997
Purchases	0	0	0	0
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	9,150	17,105	9,150	17,105
Total gains (losses) (realized/unrealized):
Included in earnings	(46)	1,114	(748)	1,108
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(46)	1,114	(748)	1,108
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	(46)	1,114	(748)	1,108
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(46)	1,114	(748)	1,108
Equity securities | Included in other comprehensive income (loss)
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
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	4	4	4	4
Purchases	0	0	0	0
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	0	4	0	4
Total gains (losses) (realized/unrealized):
Included in earnings	(4)	0	(4)	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(4)	0	(4)	0
Other invested assets | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	(4)	0	(4)	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(4)	0	(4)	0
Other invested assets | 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
Other invested assets | Included in other comprehensive income (loss)
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
Other invested assets | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Short-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	0	0	0	0
Purchases	0	463	0	463
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	0	(369)	0	(369)
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	0	94	0	94
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
Short-term investments | 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
Short-term investments | 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
Short-term investments | Included in other comprehensive income (loss)
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
Short-term investments | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Reinsurance recoverables
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	20,214,824	6,468,704	8,539,671	5,600,008
Purchases	270,556	244,013	537,507	479,391
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	19,028,138	8,485,905	19,028,138	8,485,905
Total gains (losses) (realized/unrealized):
Included in earnings	(1,457,242)	1,773,188	9,950,960	2,406,506
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(1,317,838)	1,833,209	10,102,377	2,504,883
Reinsurance recoverables | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	(1,457,242)	1,773,188	9,950,960	2,406,506
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(1,317,838)	1,833,209	10,102,377	2,504,883
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
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	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	1,575	7,792	3,135	9,261
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	(1,579)	(1,579)	(3,158)	(3,159)
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	0	6,295	0	6,295
Total gains (losses) (realized/unrealized):
Included in earnings	4	82	23	193
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	0	0	0
Receivables from parents and affiliates | 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
Receivables from parents and affiliates | 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
Receivables from parents and affiliates | Included in other comprehensive income (loss)
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
Receivables from parents and affiliates | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	4	82	23	193
Future policy benefits
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	(20,196,457)	(6,459,377)	(8,529,566)	(5,588,840)
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	(268,599)	(242,067)	(533,587)	(475,502)
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	(19,014,066)	(8,476,541)	(19,014,066)	(8,476,541)
Total gains (losses) (realized/unrealized):
Included in earnings	1,450,990	(1,775,097)	(9,950,913)	(2,412,199)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	1,319,848	(1,836,960)	(10,102,329)	(2,510,576)
Future policy benefits | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	1,450,990	(1,775,097)	(9,950,913)	(2,412,199)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	1,319,848	(1,836,960)	(10,102,329)	(2,510,576)
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
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	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	(900,261)	(53,136)	(962,351)	(13,015)
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	(67,527)	(41,906)	(123,092)	(48,413)
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	(1,045,483)	(786,969)	(1,045,483)	(786,969)
Total gains (losses) (realized/unrealized):
Included in earnings	(77,695)	(691,927)	39,960	(725,541)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(82,850)	(691,376)	42,260	(724,989)
Policyholders' account balances | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	(77,695)	(691,927)	39,960	(725,541)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(82,850)	(691,376)	42,260	(724,989)
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
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0		0
Policyholders' account balances | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	0	0	0	0
Available-for-sale | Fixed maturities | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	(2,361)	(665)	(4,140)	(3,067)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(2,361)	0	(3,695)	(3,163)
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	18,807	678	2,031	842
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	18,757		2,413
Available-for-sale | Fixed maturities | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	10	264	100	363
Available-for-sale | Fixed maturities | US government
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	42,013	32,188	38,671	29,816
Purchases	2,779	2,204	6,121	4,576
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	44,792	34,392	44,792	34,392
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 | Foreign government bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	152	164	163	0
Purchases	0	0	0	0
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	159
Transfers out of Level 3	0	0	0	0
Fair Value, end of period	161	165	161	165
Total gains (losses) (realized/unrealized):
Included in earnings	9	1	(2)	6
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	9	0	(2)	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	130,682	54,960	50,083	56,588
Purchases	1,471	791	8,664	2,122
Sales	0	(25)	(3,680)	(53)
Issuances	0	0	0	0
Settlements	(3,377)	(2,584)	(6,335)	(9,681)
Other	0	(1)	0	0
Transfers into Level 3	11,758	639	109,772	8,216
Transfers out of Level 3	0	0	0	0
Fair Value, end of period	156,972	54,014	156,972	54,014
Total gains (losses) (realized/unrealized):
Included in earnings	16,438	234	(1,532)	(3,178)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	16,378	0	(807)	(3,163)
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	7,438	79,804	2,001	6,556
Purchases	0	0	6,145	0
Sales	0	(1)	0	(2)
Issuances	0	0	0	0
Settlements	(304)	(177)	(528)	(4,156)
Other	0	0	0	0
Transfers into Level 3	0	1,700	0	77,660
Transfers out of Level 3	(5,636)	(77,071)	(5,636)	(77,071)
Fair Value, end of period	1,507	4,297	1,507	4,297
Total gains (losses) (realized/unrealized):
Included in earnings	9	42	(475)	1,310
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	9	0	(473)	0
Trading | Fixed maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	538	0	668	0
Purchases	0	0	0	0
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	751	0	751
Transfers out of Level 3	0	0	0	0
Fair Value, end of period	644	605	644	605
Total gains (losses) (realized/unrealized):
Included in earnings	106	(146)	(24)	(146)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	106	(146)	(24)	(146)
Trading | Fixed maturities | 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
Trading | Fixed maturities | Other income
Total gains (losses) (realized/unrealized):
Included in earnings	106	(146)	(24)	(146)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	106	(146)	(24)	(146)
Trading | Fixed maturities | Included in other comprehensive income (loss)
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
Trading | Fixed maturities | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	$ 0	$ 0	$ 0	$ 0