Derivative Financial Instruments and Hedging Activities - Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Notional	$ 159,814	$ 163,446
Fair Value of Assets	1,499	1,809
Fair Value of Liabilities	2,689	2,563
Fair value of assets (liabilities) available for offset	936	1,200
Other Liabilities
Derivatives, Fair Value [Line Items]
Collateral held for netting against asset positions	436	457
Other Assets
Derivatives, Fair Value [Line Items]
Collateral available for netting against liability positions	1,300	1,200
Interest rate swaps | Fair value hedges | Level 2 | Derivatives designated as hedges
Derivatives, Fair Value [Line Items]
Notional	33,285	18,379
Fair Value of Assets	4	75
Fair Value of Liabilities	456	238
Interest rate swaps | Cash flow hedges | Level 2 | Derivatives designated as hedges
Derivatives, Fair Value [Line Items]
Notional	1,964	2,381
Fair Value of Assets	21	17
Fair Value of Liabilities	3	16
Foreign currency swaps | Cash flow hedges | Level 2 | Derivatives designated as hedges
Derivatives, Fair Value [Line Items]
Notional	9,054	8,003
Fair Value of Assets	103	144
Fair Value of Liabilities	399	311
Interest rate contracts | Level 2 | Derivatives not designated as hedges
Derivatives, Fair Value [Line Items]
Notional	115,512	134,683
Fair Value of Assets	1,371	1,573
Fair Value of Liabilities	$ 1,831	$ 1,997