Activity in the ALLL by segment (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 2,457	$ 2,974
Provision for loan losses	1,398	1,523	2,708
Loan charge-offs	(1,907)	(2,241)	(3,018)
Loan recoveries	226	201	163
Balance at end of period	2,174	2,457	2,974
Commercial Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	964	1,303
Provision for loan losses	241	324
Loan charge-offs	(457)	(803)
Loan recoveries	154	140
Balance at end of period	902	964
Residential Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	1,354	1,498
Provision for loan losses	1,062	1,113
Loan charge-offs	(1,316)	(1,275)
Loan recoveries	31	18
Balance at end of period	1,131	1,354
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	139	173
Provision for loan losses	95	86
Loan charge-offs	(134)	(163)
Loan recoveries	41	43
Balance at end of period	$ 141	$ 139