Derivative Instruments (Gross Notional Amount and Fair Value of Derivatives Contracts) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Derivative [Line Items]
Assets	$ 9,144,675	$ 7,086,534
Liabilities	(18,397,841)	(12,573,983)
Derivative, Notional Amount	208,138,463	187,608,681
Derivatives Designated as Hedge Accounting Instruments:
Derivative [Line Items]
Assets	251,132	37,314
Liabilities	(319)	(6,900)
Derivative, Notional Amount	1,470,912	889,896
Derivatives Designated as Hedge Accounting Instruments: | Interest Rate Swaps
Derivative [Line Items]
Assets	0	55
Liabilities	(302)	0
Derivative, Notional Amount	3,225	3,344
Derivatives Designated as Hedge Accounting Instruments: | Foreign Currency Swaps
Derivative [Line Items]
Assets	251,132	37,259
Liabilities	(17)	(6,900)
Derivative, Notional Amount	1,467,687	886,552
Derivatives Not Qualifying as Hedge Accounting Instruments:
Derivative [Line Items]
Assets	8,893,543	7,049,220
Liabilities	(18,397,522)	(12,567,083)
Derivative, Notional Amount	206,667,551	186,718,785
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Swaps
Derivative [Line Items]
Assets	7,164,547	5,698,740
Liabilities	(16,687,241)	(10,348,130)
Derivative, Notional Amount	137,756,210	130,358,860
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Future
Derivative [Line Items]
Assets	7,133	2,876
Liabilities	(1,060)	(2,709)
Derivative, Notional Amount	2,314,100	4,109,300
Derivatives Not Qualifying as Hedge Accounting Instruments: | Foreign Currency Forwards
Derivative [Line Items]
Assets	9,396	842
Liabilities	(1,318)	(1,063)
Derivative, Notional Amount	260,555	119,653
Derivatives Not Qualifying as Hedge Accounting Instruments: | Credit Default Swaps
Derivative [Line Items]
Assets	0	24,789
Liabilities	(7,209)	0
Derivative, Notional Amount	1,614,050	306,900
Derivatives Not Qualifying as Hedge Accounting Instruments: | Foreign Currency Swaps
Derivative [Line Items]
Assets	339,553	68,477
Liabilities	(4,373)	(23,251)
Derivative, Notional Amount	2,235,760	2,139,523
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity Options
Derivative [Line Items]
Assets	311,055	902,050
Liabilities	(1,282,390)	(1,535,272)
Derivative, Notional Amount	38,312,555	19,461,881
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Option
Derivative [Line Items]
Assets	103,440	280,323
Liabilities	(231,918)	(173,863)
Derivative, Notional Amount	8,293,000	9,883,000
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Forward
Derivative [Line Items]
Assets	0	3,760
Liabilities	(1)	(991)
Derivative, Notional Amount	0	195,000
Derivatives Not Qualifying as Hedge Accounting Instruments: | Total Return Swap
Derivative [Line Items]
Assets	956,848	66,627
Liabilities	(141,162)	(475,209)
Derivative, Notional Amount	12,523,023	15,129,666
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity Future
Derivative [Line Items]
Assets	1,571	736
Liabilities	(40,850)	(6,595)
Derivative, Notional Amount	$ 3,358,298	$ 5,015,002