Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses by Portfolio Class (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 4,329	$ 4,326	$ 4,306	$ 4,375
Provision for credit losses	325	282	982	827
Loans charged off	398	372	1,210	1,135
Less recoveries of loans charged off	(83)	(80)	(263)	(268)
Net loans charged off	315	292	947	867
Other changes	(1)	(10)	(3)	(29)
Balance at end of period	4,338	4,306	4,338	4,306
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,473	1,180	1,287	1,146
Provision for credit losses	90	114	438	234
Loans charged off	104	91	322	230
Less recoveries of loans charged off	(17)	(20)	(73)	(74)
Net loans charged off	87	71	249	156
Other changes				(1)
Balance at end of period	1,476	1,223	1,476	1,223
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	748	735	724	726
Provision for credit losses	34	(10)	53	(18)
Loans charged off	9	2	19	16
Less recoveries of loans charged off	(8)	(13)	(23)	(44)
Net loans charged off	1	(11)	(4)	(28)
Balance at end of period	781	736	781	736
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	544	737	631	787
Provision for credit losses	(12)	(24)	(63)	(6)
Loans charged off	19	31	67	113
Less recoveries of loans charged off	(7)	(6)	(19)	(20)
Net loans charged off	12	25	48	93
Balance at end of period	520	688	520	688
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	643	752	743	771
Provision for credit losses	37	46	42	134
Loans charged off	84	77	243	233
Less recoveries of loans charged off	(30)	(23)	(84)	(72)
Net loans charged off	54	54	159	161
Balance at end of period	626	744	626	744
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	884	873	883	880
Provision for credit losses	178	156	514	481
Loans charged off	182	171	559	543
Less recoveries of loans charged off	(21)	(18)	(64)	(58)
Net loans charged off	161	153	495	485
Other changes			(1)
Balance at end of period	901	876	901	876
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,292	4,277	4,268	4,310
Provision for credit losses	327	282	984	825
Loans charged off	398	372	1,210	1,135
Less recoveries of loans charged off	(83)	(80)	(263)	(268)
Net loans charged off	315	292	947	867
Other changes			(1)	(1)
Balance at end of period	4,304	4,267	4,304	4,267
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	37	49	38	65
Provision for credit losses	(2)		(2)	2
Other changes	(1)	(10)	(2)	(28)
Balance at end of period	$ 34	$ 39	$ 34	$ 39