Derivative Instruments (Gross Notional Amount and Fair Value of Derivatives Contracts) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Derivative [Line Items]
Notional	$ 38,804,842	$ 39,456,440
Assets	1,470,068	1,477,909
Liabilities	(1,809,791)	(1,368,213)
Future policy benefits
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	(3,393,000)	(4,060,000)
Policyholders' account balances
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	(1,933,000)	(2,041,000)
Other assets
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	377,000	400,000
Reinsurance Recoverables (Payables)
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	1,866,000	1,881,000
Derivatives Designated as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	527,122	637,001
Assets	34,878	29,028
Liabilities	0	(1,372)
Derivatives Designated as Hedge Accounting Instruments: | Foreign Currency Swaps
Derivative [Line Items]
Notional	527,122	637,001
Assets	34,878	29,028
Liabilities	0	(1,372)
Derivatives Not Qualifying as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	38,277,720	38,819,439
Assets	1,435,190	1,448,881
Liabilities	(1,809,791)	(1,366,841)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Futures
Derivative [Line Items]
Notional	0	55,000
Assets	0	34
Liabilities	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Swaps
Derivative [Line Items]
Notional	10,513,400	10,520,230
Assets	117,862	338,731
Liabilities	(657,789)	(255,434)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Options
Derivative [Line Items]
Notional	0	0
Assets	0	0
Liabilities	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Forwards
Derivative [Line Items]
Notional	0	0
Assets	0	0
Liabilities	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Foreign Currency Forwards
Derivative [Line Items]
Notional	44,567	50,346
Assets	607	370
Liabilities	(1,250)	(536)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Foreign Currency Swaps
Derivative [Line Items]
Notional	208,153	208,153
Assets	4,295	9,711
Liabilities	(1,373)	(826)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Credit Default Swap
Derivative [Line Items]
Notional	75,000	1,745,550
Assets	4,146	48,147
Liabilities	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity Futures
Derivative [Line Items]
Notional	2,067,205	855,432
Assets	22,169	892
Liabilities	0	(1,016)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Total Return Swaps
Derivative [Line Items]
Notional	1,324,946	4,802,777
Assets	46	87,832
Liabilities	(32,225)	(80,808)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity Options
Derivative [Line Items]
Notional	24,044,449	20,581,951
Assets	1,286,065	963,164
Liabilities	$ (1,117,154)	$ (1,028,221)