Summary of Transactions in the ALLL by Portfolio segment (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Beginning Balance	$ 2,255	[1]	$ 3,004		$ 3,749
Losses charged off	(837)		(1,314)		(2,485)
Recoveries of losses previously charged off	133		142		157
Change In Accounting Principle					45
Provision For Loan Lease And Other Losses	303		423		1,538
Ending Balance	1,854	[1]	2,255	[1]	3,004
Commercial Portfolio Segment
Beginning Balance	1,527	[2]	1,989		2,517
Losses charged off	(358)		(615)		(1,444)
Recoveries of losses previously charged off	61		61		80
Provision For Loan Lease And Other Losses	6		92		836
Ending Balance	1,236	[3]	1,527	[2]	1,989
Residential Mortgage Loans
Beginning Balance	227	[2]	310		375
Losses charged off	(129)		(180)		(441)
Recoveries of losses previously charged off	7		7		2
Provision For Loan Lease And Other Losses	124		90		374
Ending Balance	229	[3]	227	[2]	310
Consumer Portfolio Segment
Beginning Balance	365	[2]	555		664
Losses charged off	(350)		(519)		(600)
Recoveries of losses previously charged off	65		74		75
Change In Accounting Principle					45
Provision For Loan Lease And Other Losses	198		255		371
Ending Balance	278	[3]	365	[2]	555
Unallocated (Member)
Beginning Balance	136	[2]	150		193
Provision For Loan Lease And Other Losses	(25)		(14)		(43)
Ending Balance	$ 111	[3]	$ 136	[2]	$ 150

[1] At December 31, 2012 and 2011, includes $0 and $30 of cash, $0 and $7 of other short-term investments, $50 and $50 of commercial mortgage loans, $0 and $223 of home equity loans, $0 and $259 of automobile loans, ($5) and ($10) of ALLL, $3 and $4 of other assets, $0 and $4 of other liabilities, $0 and $191 of long-term debt from consolidated VIEs that are included in their respective captions. See Note 10.

[2] Includes $14 related to leveraged leases.

[3] Includes $11 related to leveraged leases.