Shareholders' Equity - Adjustments to Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Class of Stock [Line Items]
Net interest income	$ (735)		$ (691)		$ (1,451)	$ (1,457)
Compensation and employee benefits expenses	1,099		1,123		2,351	2,415
Total amounts reclassified from accumulated other comprehensive income	(711)	$ (463)	(763)	$ (549)	(1,174)	(1,312)
Other comprehensive income (loss), reclassified losses into net income, tax	15		20		98	39
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, tax	14		14		(38)	27
Other comprehensive (income) loss, actuarial losses, tax					0	5
Amounts Reclassified into Earnings
Class of Stock [Line Items]
Total amounts reclassified from accumulated other comprehensive income	82		92		164	193
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Investment Securities
Class of Stock [Line Items]
Net interest income	42		54		270	106
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Cash Flow Hedges
Class of Stock [Line Items]
Net interest income	$ 40		$ 38		(107)	75
Amounts Reclassified into Earnings | Amortization of Actuarial Losses
Class of Stock [Line Items]
Compensation and employee benefits expenses					$ 1	$ 12