Derivatives and Hedging Activities - Schedule of Effect of Fair Value and Cash Flow Hedges on Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense — Long-term debt	$ (181)	$ (292)	$ (572)	$ (952)
Interest income – loans	1,466	1,516	4,310	4,578
Interest Income - securities	408	298	1,211	789
Investment banking and debt placement fees	184	171	537	467
Net gain (loss) on cash flow hedging relationships
Realized gains (losses) (pre-tax) reclassified from AOCI into net income	(98)	(187)	(283)	(602)
Interest rate | Interest expense – long-term debt | Fair Value Hedging
Net gains (losses) on fair value hedging relationships
Recognized on hedged items	(42)	(333)	(294)	(198)
Recognized on derivatives designated as hedging instruments	(2)	258	157	(22)
Net income (expense) recognized on fair value hedges	(44)	(75)	(137)	(220)
Interest rate | Interest expense – long-term debt | Cash Flow Hedging
Net gain (loss) on cash flow hedging relationships
Realized gains (losses) (pre-tax) reclassified from AOCI into net income	0	0	(2)	(1)
Net income (expense) recognized on cash flow hedges	0	0	(2)	(1)
Interest rate | Interest income – loans | Fair Value Hedging
Net gains (losses) on fair value hedging relationships
Recognized on hedged items	0	0	0	0
Recognized on derivatives designated as hedging instruments	0	0	0	0
Net income (expense) recognized on fair value hedges	0	0	0	0
Interest rate | Interest income – loans | Cash Flow Hedging
Net gain (loss) on cash flow hedging relationships
Realized gains (losses) (pre-tax) reclassified from AOCI into net income	(98)	(184)	(281)	(599)
Net income (expense) recognized on cash flow hedges	(98)	(184)	(281)	(599)
Interest rate | Interest Income - securities | Fair Value Hedging
Net gains (losses) on fair value hedging relationships
Recognized on hedged items	3	329	118	156
Recognized on derivatives designated as hedging instruments	4	(285)	(98)	(47)
Net income (expense) recognized on fair value hedges	7	44	20	109
Interest rate | Interest Income - securities | Cash Flow Hedging
Net gain (loss) on cash flow hedging relationships
Realized gains (losses) (pre-tax) reclassified from AOCI into net income	0	0	0	0
Net income (expense) recognized on cash flow hedges	0	0	0	0
Interest rate | Investment banking and debt placement fees | Fair Value Hedging
Net gains (losses) on fair value hedging relationships
Recognized on hedged items	0	0	0	0
Recognized on derivatives designated as hedging instruments	0	0	0	0
Net income (expense) recognized on fair value hedges	0	0	0	0
Interest rate | Investment banking and debt placement fees | Cash Flow Hedging
Net gain (loss) on cash flow hedging relationships
Realized gains (losses) (pre-tax) reclassified from AOCI into net income	0	(3)	0	(2)
Net income (expense) recognized on cash flow hedges	$ 0	$ (3)	$ 0	$ (2)