Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses by Portfolio Class (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 4,441	$ 4,417
Provision for credit losses	377	341
Loans charged-off	473	453
Less recoveries of loans charged-off	(106)	(112)
Net loans charged-off	367	341
Balance at end of period	4,451	4,417
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,454	1,372
Provision for credit losses	64	74
Loans charged-off	111	94
Less recoveries of loans charged-off	(38)	(34)
Net loans charged-off	73	60
Balance at end of period	1,445	1,386
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	800	831
Provision for credit losses	12	(8)
Loans charged-off	1	3
Less recoveries of loans charged-off	(1)	(6)
Net loans charged-off		(3)
Balance at end of period	812	826
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	455	449
Provision for credit losses	(7)	1
Loans charged-off	8	13
Less recoveries of loans charged-off	(5)	(6)
Net loans charged-off	3	7
Balance at end of period	445	443
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	630	678
Provision for credit losses	70	60
Loans charged-off	96	95
Less recoveries of loans charged-off	(30)	(29)
Net loans charged-off	66	66
Balance at end of period	634	672
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,102	1,056
Provision for credit losses	238	219
Loans charged-off	257	248
Less recoveries of loans charged-off	(32)	(37)
Net loans charged-off	225	211
Balance at end of period	$ 1,115	1,064
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		31
Provision for credit losses		(5)
Balance at end of period		$ 26