Derivative Financial Instruments - Schedule of Outstanding Hedges: (Notional Amount) (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Derivatives not designated as hedging instruments \| Interest rate contracts \| Futures
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	$ 40,050	$ 97,035
Derivatives not designated as hedging instruments \| Foreign exchange contracts \| Futures
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	165	472
Derivatives not designated as hedging instruments \| Foreign exchange contracts \| Forward, swap and spot
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	3,369,461	2,768,458
Derivatives not designated as hedging instruments \| Foreign exchange contracts \| Options purchased
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	2,321	436
Derivatives not designated as hedging instruments \| Foreign exchange contracts \| Options written
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	1,675	110
Derivatives not designated as hedging instruments \| Other derivative contracts \| Futures
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	226	159
Derivatives not designated as hedging instruments \| Other derivative contracts \| Stable value contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	10,366	12,271
Derivatives not designated as hedging instruments \| Other derivative contracts \| Deferred value awards
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	169	222
Derivatives designated as hedging instruments \| Interest rate contracts \| Swap agreements
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	43,136	42,708
Derivatives designated as hedging instruments \| Foreign exchange contracts \| Forward and swap
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instruments	$ 13,852	$ 12,350