Derivative Instruments (Gross Notional Amount and Fair Value of Derivatives Contracts) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Gross Notional	$ 266,639,029	$ 196,977,180
Fair Value Assets	9,045,737	7,685,050
Fair Value Liabilities	(21,248,026)	(18,654,072)
Derivatives Designated as Hedge Accounting Instruments:
Derivative [Line Items]
Gross Notional	2,277,700	1,936,568
Fair Value Assets	121,243	233,812
Fair Value Liabilities	(54,282)	(10,778)
Derivatives Designated as Hedge Accounting Instruments: \| Interest Rate Swaps
Derivative [Line Items]
Gross Notional	3,064	3,225
Fair Value Assets	0	0
Fair Value Liabilities	(238)	(316)
Derivatives Designated as Hedge Accounting Instruments: \| Foreign Currency Swaps
Derivative [Line Items]
Gross Notional	2,274,636	1,933,343
Fair Value Assets	121,243	233,812
Fair Value Liabilities	(54,044)	(10,462)
Derivatives Not Qualifying as Hedge Accounting Instruments:
Derivative [Line Items]
Gross Notional	264,361,329	195,040,612
Fair Value Assets	8,924,494	7,451,238
Fair Value Liabilities	(21,193,744)	(18,643,294)
Derivatives Not Qualifying as Hedge Accounting Instruments: \| Interest Rate Swaps
Derivative [Line Items]
Gross Notional	163,179,764	138,419,110
Fair Value Assets	6,605,817	6,757,890
Fair Value Liabilities	(17,820,436)	(17,092,749)
Derivatives Not Qualifying as Hedge Accounting Instruments: \| Interest Rate Future
Derivative [Line Items]
Gross Notional	1,332,600	2,425,500
Fair Value Assets	3,055	3,267
Fair Value Liabilities	(210)	(201)
Derivatives Not Qualifying as Hedge Accounting Instruments: \| Foreign Currency Forwards
Derivative [Line Items]
Gross Notional	744,576	364,946
Fair Value Assets	1,772	590
Fair Value Liabilities	(12,232)	(10,423)
Derivatives Not Qualifying as Hedge Accounting Instruments: \| Credit Default Swaps
Derivative [Line Items]
Gross Notional	643,280	47,450
Fair Value Assets	7,727	346
Fair Value Liabilities	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: \| Foreign Currency Swaps
Derivative [Line Items]
Gross Notional	2,237,331	2,289,170
Fair Value Assets	96,618	194,412
Fair Value Liabilities	(31,294)	(14,624)
Derivatives Not Qualifying as Hedge Accounting Instruments: \| Equity Options
Derivative [Line Items]
Gross Notional	49,247,510	25,187,516
Fair Value Assets	1,600,335	239,003
Fair Value Liabilities	(1,552,706)	(1,112,196)
Derivatives Not Qualifying as Hedge Accounting Instruments: \| interest rate forward
Derivative [Line Items]
Gross Notional	1,458,000	1,104,000
Fair Value Assets	741	11,265
Fair Value Liabilities	(3,196)	(12,359)
Derivatives Not Qualifying as Hedge Accounting Instruments: \| Interest Rate Option
Derivative [Line Items]
Gross Notional	29,738,000	8,368,000
Fair Value Assets	189,112	123,168
Fair Value Liabilities	(969,718)	(225,125)
Derivatives Not Qualifying as Hedge Accounting Instruments: \| Total Return Swap
Derivative [Line Items]
Gross Notional	15,049,993	15,958,130
Fair Value Assets	418,084	120,341
Fair Value Liabilities	(803,452)	(175,104)
Derivatives Not Qualifying as Hedge Accounting Instruments: \| Equity Futures
Derivative [Line Items]
Gross Notional	418,973	876,790
Fair Value Assets	1,232	956
Fair Value Liabilities	(500)	(513)
Derivatives Not Qualifying as Hedge Accounting Instruments: \| Synthetic Gics
Derivative [Line Items]
Gross Notional	311,302	0
Fair Value Assets	1	0
Fair Value Liabilities	$ 0	$ 0

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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