Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses by Portfolio Type (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 4,320	$ 4,351	$ 4,306	$ 4,375
Provision for credit losses	327	281	657	545
Loans charged off	407	380	812	763
Less recoveries of loans charged off	(90)	(84)	(180)	(188)
Net loans charged off	317	296	632	575
Other changes	(1)	(10)	(2)	(19)
Balance at end of period	4,329	4,326	4,329	4,326
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,441	1,200	1,287	1,146
Provision for credit losses	111	22	348	120
Loans charged off	107	65	218	139
Less recoveries of loans charged off	(28)	(23)	(56)	(54)
Net loans charged off	79	42	162	85
Other changes				(1)
Balance at end of period	1,473	1,180	1,473	1,180
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	734	721	724	726
Provision for credit losses	14	15	19	(8)
Loans charged off	7	9	10	14
Less recoveries of loans charged off	(7)	(8)	(15)	(31)
Net loans charged off		1	(5)	(17)
Balance at end of period	748	735	748	735
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	556	764	631	787
Provision for credit losses	5	6	(51)	18
Loans charged off	25	41	48	82
Less recoveries of loans charged off	(8)	(8)	(12)	(14)
Net loans charged off	17	33	36	68
Balance at end of period	544	737	544	737
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	678	738	743	771
Provision for credit losses	16	65	5	88
Loans charged off	79	75	159	156
Less recoveries of loans charged off	(28)	(24)	(54)	(49)
Net loans charged off	51	51	105	107
Balance at end of period	643	752	643	752
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	875	871	883	880
Provision for credit losses	179	171	336	325
Loans charged off	189	190	377	372
Less recoveries of loans charged off	(19)	(21)	(43)	(40)
Net loans charged off	170	169	334	332
Other changes			(1)
Balance at end of period	884	873	884	873
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,284	4,294	4,268	4,310
Provision for credit losses	325	279	657	543
Loans charged off	407	380	812	763
Less recoveries of loans charged off	(90)	(84)	(180)	(188)
Net loans charged off	317	296	632	575
Other changes			(1)	(1)
Balance at end of period	4,292	4,277	4,292	4,277
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	36	57	38	65
Provision for credit losses	2	2		2
Other changes	(1)	(10)	(1)	(18)
Balance at end of period	$ 37	$ 49	$ 37	$ 49