Shareholders' Equity - Adjustments to Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Class of Stock [Line Items]
Net interest income	$ (835)	$ (714)
Compensation and employee benefits expenses	1,441	1,262
Net income	(764)	(644)
Income tax expense	(205)	(178)
Amounts Reclassified into Earnings
Class of Stock [Line Items]
Net income	33	56
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Investment Securities
Class of Stock [Line Items]
Gains (losses) from sales of available-for-sale securities, net	(1)	0
Net interest income	14	27
Net realized gains from sales of available-for-sale securities, tax	0	20
Amortization of net unrealized gain (loss), before adjustment, tax	5	0
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Cash Flow Hedges
Class of Stock [Line Items]
Net interest income	20	29
Net realized gains from sales of available-for-sale securities, tax	$ 6	$ 8