Fair Value of Assets and Liabilities (Changes in Level 3 Assets and Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Equity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	$ 515	$ 4,153
Purchases	15	0
Sales	0	0
Issuances	0	0
Settlements	0	0
Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, end of period	592	4,166
Total gains (losses) (realized/unrealized):
Included in earnings	62	13
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	62	13
Equity Securities | 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
Equity Securities | Other income
Total gains (losses) (realized/unrealized):
Included in earnings	62	13
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	62	13
Equity Securities | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	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
Short-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	12,554	10,000
Purchases	0	2,349
Sales	0	0
Issuances	0	0
Settlements	(12,554)	0
Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, end of period	0	12,349
Total gains (losses) (realized/unrealized):
Included in earnings	0	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	0
Cash equivalents
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	7,776	0
Purchases	0	100
Sales	0	0
Issuances	0	0
Settlements	(7,776)	0
Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, end of period	0	100
Total gains (losses) (realized/unrealized):
Included in earnings	0	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	0
Other assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	400,441	53,980
Purchases	13,292	2,653
Sales	0	0
Issuances	0	0
Settlements	(15,558)	(2,133)
Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, end of period	376,898	63,072
Total gains (losses) (realized/unrealized):
Included in earnings	(21,277)	8,572
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(5,720)	6,439
Other assets | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	(21,277)	8,572
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(5,720)	6,439
Other 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 assets | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	0	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	0
Other assets | 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	1,881,030	409,013
Purchases	4,097	4,262
Sales	0	0
Issuances	0	0
Settlements	19,290	0
Other	(239,022)	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, end of period	1,866,253	271,390
Total gains (losses) (realized/unrealized):
Included in earnings	200,858	(141,885)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	222,445	(135,675)
Reinsurance recoverables | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	200,858	(141,885)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	222,445	(135,675)
Reinsurance recoverables | 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 recoverables | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	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
Future policy benefits
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	(4,060,214)	(17,314,004)
Purchases	0	0
Sales	0	0
Issuances	(47,577)	(291,149)
Settlements	0	0
Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, end of period	(3,392,954)	(10,511,815)
Total gains (losses) (realized/unrealized):
Included in earnings	714,837	7,093,338
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	685,633	6,900,120
Future policy benefits | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	714,837	7,093,338
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	685,633	6,900,120
Future policy benefits | 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
Future policy benefits | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	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
Policyholders' account balances
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	(2,040,532)	(580,184)
Purchases	0	0
Sales	0	0
Issuances	0	(138,525)
Settlements	(17,426)	0
Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, end of period	(1,933,466)	(986,479)
Total gains (losses) (realized/unrealized):
Included in earnings	124,492	(267,770)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	89,242	(252,703)
Policyholders' account balances | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	124,492	(267,770)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	89,242	(252,703)
Policyholders' account balances | 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
Policyholders' account balances | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	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
Available-for-sale | Fixed maturities | Realized investment gains (losses), net
Total gains (losses) (realized/unrealized):
Included in earnings	(303)	(44)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(352)	(37)
Available-for-sale | Fixed maturities | 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
Available-for-sale | Fixed maturities | Included in other comprehensive income (loss)
Total gains (losses) (realized/unrealized):
Included in earnings	(12,455)	(987)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(12,449)	(1,100)
Available-for-sale | Fixed maturities | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	35	(7)
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	0	15,000
Purchases	0	0
Sales	0	0
Issuances	0	0
Settlements	0	0
Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, end of period	0	15,000
Total gains (losses) (realized/unrealized):
Included in earnings	0	0
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	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	190,075	148,687
Purchases	5,000	10,634
Sales	(4,060)	0
Issuances	0	0
Settlements	(2,334)	(7,627)
Other	0	0
Transfers into Level 3	0	15,147
Transfers out of Level 3	0	0
Fair Value, end of period	179,763	165,910
Total gains (losses) (realized/unrealized):
Included in earnings	(8,918)	(931)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(8,948)	(1,031)
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	75,811	18,542
Purchases	0	0
Sales	(10,000)	0
Issuances	0	0
Settlements	(1,656)	(1,479)
Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	(13,000)	0
Fair Value, end of period	47,350	16,956
Total gains (losses) (realized/unrealized):
Included in earnings	(3,805)	(107)
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	(3,853)	(106)
Trading | Fixed maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning of period	0	5,045
Purchases	0	0
Sales	0	0
Issuances	0	0
Settlements	0	0
Other	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, end of period	0	5,127
Total gains (losses) (realized/unrealized):
Included in earnings	0	82
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	87
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	0	88
Unrealized gains (losses) for assets/liabilities still held:
Included in earnings	0	87
Trading | Fixed maturities | Included in other comprehensive income (loss)
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 | Net investment income
Total gains (losses) (realized/unrealized):
Included in earnings	$ 0	$ (6)