Activity in the ALLL by segment (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 2,457	$ 2,974
Provision for loan losses	313	451
Loan charge-offs	(463)	(615)
Loan recoveries	41	44
Balance at end of period	2,348	2,854
Commercial Portfolio Segment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	964	1,303
Provision for loan losses	38	108
Loan charge-offs	(126)	(185)
Loan recoveries	25	29
Balance at end of period	901	1,255
Residential Mortgage Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	1,354	1,498
Provision for loan losses	258	322
Loan charge-offs	(302)	(385)
Loan recoveries	5	5
Balance at end of period	1,315	1,440
Consumer Portfolio Segment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	139	173
Provision for loan losses	17	21
Loan charge-offs	(35)	(45)
Loan recoveries	11	10
Balance at end of period	$ 132	$ 159