Derivative Instruments (Gross Notional Amount and Fair Value of Derivatives Contracts) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Notional	$ 39,456,440	$ 200,749,958
Assets	1,477,909	14,819,236
Liabilities	(1,368,213)	(11,952,846)
Future Policy Benefits
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	(4,060,000)	(17,314,000)
Policyholders' account balances
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	(2,041,000)	(580,000)
Other assets
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	400,000	54,000
Other liabilities
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	0	(35,000)
Reinsurance Recoverables (Payables)
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	1,881,000	471,000
Derivatives Designated as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	637,001	1,376,290
Assets	29,028	23,167
Liabilities	(1,372)	(82,625)
Derivatives Designated as Hedge Accounting Instruments: | Foreign Currency Swaps
Derivative [Line Items]
Notional	637,001	1,376,290
Assets	29,028	23,167
Liabilities	(1,372)	(82,625)
Derivatives Not Qualifying as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	38,819,439	199,373,668
Assets	1,448,881	14,796,069
Liabilities	(1,366,841)	(11,870,221)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Futures
Derivative [Line Items]
Notional	55,000	4,597,200
Assets	34	2,755
Liabilities	0	(1,621)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Swaps
Derivative [Line Items]
Notional	10,520,230	131,129,200
Assets	338,731	12,448,036
Liabilities	(255,434)	(9,540,941)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Option
Derivative [Line Items]
Notional	0	10,198,000
Assets	0	608,538
Liabilities	0	(178,563)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Forwards
Derivative [Line Items]
Notional	0	75,000
Assets	0	464
Liabilities	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Foreign Currency Forwards
Derivative [Line Items]
Notional	50,346	34,988
Assets	370	4
Liabilities	(536)	(557)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Foreign Currency Swaps
Derivative [Line Items]
Notional	208,153	228,117
Assets	9,711	7,939
Liabilities	(826)	(8,440)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Credit Default Swap
Derivative [Line Items]
Notional	1,745,550	1,574,173
Assets	48,147	38,875
Liabilities	0	(52)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity Future
Derivative [Line Items]
Notional	855,432	5,558,882
Assets	892	9,424
Liabilities	(1,016)	(24,688)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Total Return Swaps
Derivative [Line Items]
Notional	4,802,777	22,121,729
Assets	87,832	62,362
Liabilities	(80,808)	(1,162,907)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity Options
Derivative [Line Items]
Notional	20,581,951	23,856,379
Assets	963,164	1,617,672
Liabilities	$ (1,028,221)	$ (952,452)