Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses by Portfolio Type (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 4,306	$ 4,375
Provision for credit losses	330	264
Loans charged off	405	383
Less recoveries of loans charged off	(90)	(104)
Net loans charged off	315	279
Other changes	(1)	(9)
Balance at end of period	4,320	4,351
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,287	1,146
Provision for credit losses	237	98
Loans charged off	111	74
Less recoveries of loans charged off	(28)	(31)
Net loans charged off	83	43
Other changes		(1)
Balance at end of period	1,441	1,200
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	724	726
Provision for credit losses	5	(23)
Loans charged off	3	5
Less recoveries of loans charged off	(8)	(23)
Net loans charged off	(5)	(18)
Balance at end of period	734	721
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	631	787
Provision for credit losses	(56)	12
Loans charged off	23	41
Less recoveries of loans charged off	(4)	(6)
Net loans charged off	19	35
Balance at end of period	556	764
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	743	771
Provision for credit losses	(11)	23
Loans charged off	80	81
Less recoveries of loans charged off	(26)	(25)
Net loans charged off	54	56
Balance at end of period	678	738
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	883	880
Provision for credit losses	157	154
Loans charged off	188	182
Less recoveries of loans charged off	(24)	(19)
Net loans charged off	164	163
Other changes	(1)
Balance at end of period	875	871
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,268	4,310
Provision for credit losses	332	264
Loans charged off	405	383
Less recoveries of loans charged off	(90)	(104)
Net loans charged off	315	279
Other changes	(1)	(1)
Balance at end of period	4,284	4,294
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	38	65
Provision for credit losses	(2)
Other changes		(8)
Balance at end of period	$ 36	$ 57