Activity in the ALLL by segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 1,834	$ 2,003	$ 1,937	$ 2,044
Provision for loan losses	23	93	107	275
Allowance for Loan and Lease Losses, Write-offs	(102)	(164)	(356)	(473)
Loan recoveries	31	36	98	122
Balance at end of period	1,786	1,968	1,786	1,968
Commercial Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	993	958	986	946
Provision for loan losses	33	25	74	82
Allowance for Loan and Lease Losses, Write-offs	(23)	(26)	(82)	(97)
Loan recoveries	10	14	35	40
Balance at end of period	1,013	971	1,013	971
Residential Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	676	875	777	930
Provision for loan losses	(39)	34	(30)	114
Allowance for Loan and Lease Losses, Write-offs	(47)	(104)	(177)	(279)
Loan recoveries	11	12	31	52
Balance at end of period	601	817	601	817
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	165	170	174	168
Provision for loan losses	29	34	63	79
Allowance for Loan and Lease Losses, Write-offs	(32)	(34)	(97)	(97)
Loan recoveries	10	10	32	30
Balance at end of period	$ 172	$ 180	$ 172	$ 180