Shareholders' Equity - Adjustments to Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Class of Stock [Line Items]
Other comprehensive income (loss), reclassification adjustment from AOCI for sale of securities, tax	$ 21			$ 81			$ 21	$ 81
Other comprehensive income (loss), reclassified losses into net income, tax	15			22			113	61
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, tax	13			14			(25)	42
Other comprehensive (income) loss, actuarial losses, tax							0	5
Net gains (losses) from sales of available-for-sale securities	(80)			(294)			(80)	(294)
Net interest income	(723)			(624)			(2,174)	(2,081)
Compensation and employee benefits expenses	1,134			1,082			3,485	3,497
Total amounts reclassified from accumulated other comprehensive income	(730)	$ (711)	$ (463)	(422)	$ (763)	$ (549)	(1,904)	(1,734)
Amounts Reclassified into Earnings
Class of Stock [Line Items]
Net gains (losses) from sales of available-for-sale securities	59			213			59	213
Total amounts reclassified from accumulated other comprehensive income	139			311			303	503
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Investment Securities
Class of Stock [Line Items]
Net interest income	42			59			312	165
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Cash Flow Hedges
Class of Stock [Line Items]
Net interest income	$ 38			$ 39			(69)	113
Amounts Reclassified into Earnings | Amortization of Actuarial Losses
Class of Stock [Line Items]
Compensation and employee benefits expenses							$ 1	$ 12