Summary of Transactions in the ALLL by Portfolio 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
Beginning Balance	$ 2,016		$ 2,614		$ 2,255	[1]	$ 3,004
Losses charged off	(188)		(294)		(660)		(1,034)
Recoveries of losses previously charged off	32		32		103		101
Provision for loan and lease losses	65		87		227		368
Ending Balance	1,925	[1]	2,439	[1]	1,925	[1]	2,439	[1]
Commercial Portfolio Segment
Beginning Balance	1,347		1,764		1,527	[2]	1,989
Losses charged off	(76)		(146)		(289)		(480)
Recoveries of losses previously charged off	14		10		47		39
Provision for loan and lease losses	2		21		2		101
Ending Balance	1,287	[3]	1,649	[2]	1,287	[3]	1,649	[2]
Residential Mortgage Loans
Beginning Balance	232		268		227	[2]	310
Losses charged off	(28)		(38)		(104)		(142)
Recoveries of losses previously charged off	2		2		5		5
Provision for loan and lease losses	26		1		104		60
Ending Balance	232	[3]	233	[2]	232	[3]	233	[2]
Consumer Portfolio Segment
Beginning Balance	316		452		365	[2]	555
Losses charged off	(84)		(110)		(267)		(412)
Recoveries of losses previously charged off	16		20		51		57
Provision for loan and lease losses	42		46		141		208
Ending Balance	290	[3]	408	[2]	290	[3]	408	[2]
Unallocated (Member)
Beginning Balance	121		130		136	[2]	150
Provision for loan and lease losses	(5)		19		(20)		(1)
Ending Balance	$ 116	[3]	$ 149	[2]	$ 116	[3]	$ 149	[2]

[1] Includes $0, $30 and $35 of cash, $0, $7 and $7of other short-term investments, $50, $50 and $29 of commercial mortgage loans, $0, $223 and $228 of home equity loans, $0, $259 and $334 of automobile loans, ($2), ($10) and ($10) of ALLL, $3, $4 and $3 of other assets, $0, $4 and $5 of other liabilities, $0, $191and $270 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2012, December 31, 2011 and September 30, 2011, respectively. See Note 8.

[2] Includes $14 related to leveraged leases.

[3] Includes $12 related to leveraged leases.