Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses by Portfolio Type (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 4,375	$ 4,537
Provision for credit losses	264	306
Loans charged off	383	422
Less recoveries of loans charged off	(104)	(81)
Net loans charged off	279	341
Other changes	(9)	(5)
Balance at end of period	4,351	4,497
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,146	1,075
Provision for credit losses	98	52
Loans charged off	74	63
Less recoveries of loans charged off	(31)	(27)
Net loans charged off	43	36
Other changes	(1)
Balance at end of period	1,200	1,091
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	726	776
Provision for credit losses	(23)	(37)
Loans charged off	5	8
Less recoveries of loans charged off	(23)	(11)
Net loans charged off	(18)	(3)
Balance at end of period	721	742
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	787	875
Provision for credit losses	12	44
Loans charged off	41	61
Less recoveries of loans charged off	(6)	(4)
Net loans charged off	35	57
Balance at end of period	764	862
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	880	884
Provision for credit losses	154	170
Loans charged off	182	184
Less recoveries of loans charged off	(19)	(14)
Net loans charged off	163	170
Balance at end of period	871	884
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	771	781
Provision for credit losses	23	80
Loans charged off	81	100
Less recoveries of loans charged off	(25)	(24)
Net loans charged off	56	76
Balance at end of period	738	785
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,310	4,391
Provision for credit losses	264	309
Loans charged off	383	416
Less recoveries of loans charged off	(104)	(80)
Net loans charged off	279	336
Other changes	(1)
Balance at end of period	4,294	4,364
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	65	146
Provision for credit losses		(3)
Loans charged off		6
Less recoveries of loans charged off		(1)
Net loans charged off		5
Other changes	(8)	(5)
Balance at end of period	$ 57	$ 133