Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses by Portfolio Class (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 4,451	$ 4,417	$ 4,441	$ 4,417
Provision for credit losses	365	327	742	668
Loans charged-off	464	437	937	890
Less recoveries of loans charged-off	(114)	(105)	(220)	(217)
Net loans charged-off	350	332	717	673
Other changes		(1)		(1)
Balance at end of period	4,466	4,411	4,466	4,411
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,445	1,386	1,454	1,372
Provision for credit losses	78	63	142	137
Loans charged-off	98	83	209	177
Less recoveries of loans charged-off	(39)	(25)	(77)	(59)
Net loans charged-off	59	58	132	118
Balance at end of period	1,464	1,391	1,464	1,391
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	812	826	800	831
Provision for credit losses	(17)	(14)	(5)	(22)
Loans charged-off	3	2	4	5
Less recoveries of loans charged-off	(2)	(2)	(3)	(8)
Net loans charged-off	1		1	(3)
Balance at end of period	794	812	794	812
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	445	443	455	449
Provision for credit losses	(3)	(3)	(10)	(2)
Loans charged-off	11	12	19	25
Less recoveries of loans charged-off	(7)	(8)	(12)	(14)
Net loans charged-off	4	4	7	11
Balance at end of period	438	436	438	436
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	634	672	630	678
Provision for credit losses	63	55	133	115
Loans charged-off	90	92	186	187
Less recoveries of loans charged-off	(31)	(32)	(61)	(61)
Net loans charged-off	59	60	125	126
Balance at end of period	638	667	638	667
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,115	1,064	1,102	1,056
Provision for credit losses	244	228	482	447
Loans charged-off	262	248	519	496
Less recoveries of loans charged-off	(35)	(38)	(67)	(75)
Net loans charged-off	227	210	452	421
Balance at end of period	$ 1,132	1,082	$ 1,132	1,082
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		26		31
Provision for credit losses		(2)		(7)
Other changes		(1)		(1)
Balance at end of period		$ 23		$ 23