Shareholders' Equity - Adjustments to Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Class of Stock [Line Items]
Gains (losses) from sales of available-for-sale securities, net	$ (294)			$ 0			$ (294)	$ (2)
Net interest income	(624)			(660)			(2,081)	(1,753)
Compensation and employee benefits expenses	1,082			1,042			3,497	3,320
Total amounts reclassified from accumulated other comprehensive income	(422)	$ (763)	$ (549)	(690)	$ (747)	$ (604)	(1,734)	(2,041)
Other comprehensive income (loss), reclassification adjustment from AOCI for sale of securities, tax	81			81			0	1
Other comprehensive income (loss), reclassified losses into net income, tax	22			31			61	22
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, tax	14			6			42	(3)
Other comprehensive (income) loss, actuarial losses, tax	0			1			5	8
Amounts Reclassified into Earnings
Class of Stock [Line Items]
Gains (losses) from sales of available-for-sale securities, net	213			0			213	1
Total amounts reclassified from accumulated other comprehensive income	311			78			503	97
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Investment Securities
Class of Stock [Line Items]
Net interest income	(59)			(60)			(165)	(83)
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Cash Flow Hedges
Class of Stock [Line Items]
Net interest income	39			16			(113)	6
Amounts Reclassified into Earnings | Amortization of Actuarial Losses
Class of Stock [Line Items]
Compensation and employee benefits expenses	$ 0			$ 2			$ 12	$ 19