Activity in the ALLL by segment (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 2,152	$ 2,348	$ 2,174	$ 2,457
Provision for loan losses	152	302	356	615
Loan charge-offs	(233)	(397)	(506)	(860)
Loan recoveries	(54)	(47)	(101)	88
Balance at end of period	2,125	2,300	2,125	2,300
Commercial Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	921	901	902	964
Provision for loan losses	42	49	106	87
Loan charge-offs	(64)	(94)	(124)	(220)
Loan recoveries	(20)	(31)	(35)	(56)
Balance at end of period	919	887	919	887
Residential Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	1,087	1,315	1,131	1,354
Provision for loan losses	78	230	190	488
Loan charge-offs	(143)	(274)	(321)	(576)
Loan recoveries	(24)	(6)	(46)	(11)
Balance at end of period	1,046	1,277	1,046	1,277
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	144	132	141	139
Provision for loan losses	32	23	60	40
Loan charge-offs	(26)	(29)	(61)	(64)
Loan recoveries	(10)	(10)	(20)	(21)
Balance at end of period	$ 160	$ 136	$ 160	$ 136