Shareholders' Equity - Adjustments to Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Class of Stock [Line Items]
Net interest income	$ (716)	$ (766)
Compensation and employee benefits expenses	1,252	1,292
Total amounts reclassified from accumulated other comprehensive income	(463)	(549)
Other comprehensive income (loss), reclassified losses into net income, tax	83	19
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, tax	(52)	14
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	101
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Investment Securities
Class of Stock [Line Items]
Net interest income	(228)	(52)
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Cash Flow Hedges
Class of Stock [Line Items]
Net interest income	(147)	37
Amounts Reclassified into Earnings | Amortization of Actuarial Losses
Class of Stock [Line Items]
Compensation and employee benefits expenses	$ 1	$ 12