Activity in the ALLL by segment (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 2,300	$ 2,744	$ 2,457	$ 2,974
Provision for loan losses	450	348	1,065	1,194
Loan charge-offs	(585)	(536)	(1,445)	(1,714)
Loan recoveries	74	44	162	146
Balance at end of period	2,239	2,600	2,239	2,600
Commercial Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	887	1,200	964	1,303
Provision for loan losses	127	86	214	318
Loan charge-offs	(126)	(214)	(346)	(619)
Loan recoveries	55	29	111	99
Balance at end of period	943	1,101	943	1,101
Residential Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	1,277	1,395	1,354	1,498
Provision for loan losses	300	236	788	810
Loan charge-offs	(425)	(282)	(1,001)	(970)
Loan recoveries	10	3	21	14
Balance at end of period	1,162	1,352	1,162	1,352
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	136	149	139	173
Provision for loan losses	23	26	63	66
Loan charge-offs	(34)	(40)	(98)	(125)
Loan recoveries	9	12	30	33
Balance at end of period	$ 134	$ 147	$ 134	$ 147