Shareholders' Equity - Adjustments to Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Class of Stock [Line Items]
Income tax expense	$ 178	$ 135
Net interest income	714	716
Compensation and employee benefits expenses	(1,262)	(1,252)
Net income	644	463
Amounts Reclassified into Earnings
Class of Stock [Line Items]
Net income	56	82
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Investment Securities
Class of Stock [Line Items]
Income tax expense	20	83
Net interest income	27	228
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Cash Flow Hedges
Class of Stock [Line Items]
Income tax expense	8	(52)
Net interest income	29	(147)
Amounts Reclassified into Earnings | Amortization of Actuarial Losses
Class of Stock [Line Items]
Income tax expense	0	0
Compensation and employee benefits expenses	$ 0	$ 1