Shareholders' Equity - Adjustments to Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Gains (losses) from sales of available-for-sale securities, net	$ (1)	$ 9	$ (39)
Net interest income	2,566	2,671	2,304
Compensation and employee benefits expenses	4,541	4,780	4,394
Net income	2,242	2,593	$ 2,156
Reclassification out of Accumulated Other Comprehensive Income
Class of Stock [Line Items]
Net income	(5)	51
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains (Losses) on Available-for-Sale Securities
Class of Stock [Line Items]
Gains (losses) from sales of available-for-sale securities, net	0	7
Net realized gains from sales of available-for-sale securities, taxes	0	(2)
Reclassification out of Accumulated Other Comprehensive Income | Other-Than-Temporary Impairment on Securities
Class of Stock [Line Items]
Losses reclassified (from) to other comprehensive income	(1)	(2)
Other-than-temporary impairment on held-to-maturity securities related to factors other than credit, taxes	0	1
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains (Losses) on Cash Flow Hedges
Class of Stock [Line Items]
Net interest income	12	19
Gain (loss) from cash flow hedge reclassified from accumulated other comprehensive income, taxes	5	7
Reclassification out of Accumulated Other Comprehensive Income | Amortization of Actuarial Losses
Class of Stock [Line Items]
Compensation and employee benefits expenses	(16)	27
Amortization of actuarial losses, taxes	$ (8)	$ 8