Derivative Financial Instruments - Schedule of Outstanding Hedges: (Notional Amount) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Derivatives not designated as hedging instruments | Interest rate contracts | Futures
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	$ 10,698	$ 9,604
Derivatives not designated as hedging instruments | Foreign exchange contracts | Futures
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	1,980	2,359
Derivatives not designated as hedging instruments | Foreign exchange contracts | Forward, swap and spot
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	2,523,696	2,569,449
Derivatives not designated as hedging instruments | Foreign exchange contracts | Options purchased
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	911	328
Derivatives not designated as hedging instruments | Foreign exchange contracts | Options written
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	460	210
Derivatives not designated as hedging instruments | Other derivative contracts | Stable value contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	33,343	32,868
Derivatives not designated as hedging instruments | Other derivative contracts | Deferred value awards
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	423	308
Derivatives designated as hedging instruments | Interest rate contracts | Swap agreements
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	21,155	15,100
Derivatives designated as hedging instruments | Foreign exchange contracts | Forward and swap
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	$ 6,840	$ 6,700