Activity in the ALLL by segment (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 2,174	$ 2,457
Provision for loan losses	204	313
Loan charge-offs	(273)	(463)
Loan recoveries	47	41
Balance at end of period	2,152	2,348
Commercial Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	902	964
Provision for loan losses	64	38
Loan charge-offs	(60)	(126)
Loan recoveries	15	25
Balance at end of period	921	901
Residential Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	1,131	1,354
Provision for loan losses	112	258
Loan charge-offs	(178)	(302)
Loan recoveries	22	5
Balance at end of period	1,087	1,315
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	141	139
Provision for loan losses	28	17
Loan charge-offs	(35)	(35)
Loan recoveries	10	11
Balance at end of period	$ 144	$ 132