Shareholders' Equity - Adjustments to Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022
Class of Stock [Line Items]
Gains (losses) from sales of available-for-sale securities, net	$ 0		$ (1)		$ 0	$ (2)
Net interest income	(691)		(584)		(1,457)	(1,093)
Compensation and employee benefits expenses	1,123		1,046		2,415	2,278
Total amounts reclassified from accumulated other comprehensive income	(763)	$ (549)	(747)	$ (604)	(1,312)	(1,351)
Other comprehensive income (loss), reclassification adjustment from AOCI for sale of securities, tax					0	0
Other comprehensive income (loss), reclassified losses into net income, tax	13		39		20	9
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification, tax	27		3		14	9
Other comprehensive (income) loss, actuarial losses, tax	5		1		0	7
Amounts Reclassified into Earnings
Class of Stock [Line Items]
Gains (losses) from sales of available-for-sale securities, net	0		1		0	1
Total amounts reclassified from accumulated other comprehensive income	92		31		193	19
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Investment Securities
Class of Stock [Line Items]
Net interest income	(54)		(34)		(106)	(23)
Amounts Reclassified into Earnings | Net Unrealized Gains (Losses) on Cash Flow Hedges
Class of Stock [Line Items]
Net interest income	38		(6)		(75)	22
Amounts Reclassified into Earnings | Amortization of Actuarial Losses
Class of Stock [Line Items]
Compensation and employee benefits expenses	$ 0		$ 2		$ 12	$ 17