Shareholders' Equity - Adjustments to Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Class of Stock [Line Items]
Gains (losses) from sales of available-for-sale securities, net	$ (294)	$ (2)	$ 57
Net interest income	2,759	2,544	1,905
Compensation and employee benefits expenses	4,744	4,428	4,554
Net income	1,944	2,774	2,693
Net realized gains from sales of available-for-sale securities, tax	81	1	(15)
Amortization of net unrealized gain (loss), before adjustment, tax	81	96	0
Net realized gains from sales of available-for-sale securities, tax	55	(13)	(25)
Other comprehensive (income) loss, actuarial losses, tax	0	(1)	16
Reclassification out of Accumulated Other Comprehensive Income
Class of Stock [Line Items]
Net income	582	122	(65)
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains (Losses) on Investment Securities
Class of Stock [Line Items]
Gains (losses) from sales of available-for-sale securities, net	213	1	(42)
Reclassification out of Accumulated Other Comprehensive Income | AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Transferred to Held-To-Maturity, Parent
Class of Stock [Line Items]
Net interest income	215	169	0
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains (Losses) on Cash Flow Hedges
Class of Stock [Line Items]
Net interest income	153	(36)	(70)
Reclassification out of Accumulated Other Comprehensive Income | Amortization of Actuarial Losses
Class of Stock [Line Items]
Compensation and employee benefits expenses	$ 1	$ (12)	$ 47