Derivative Financial Instruments - Gains and Losses on Hedged Items in Fair Value Hedges (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
Interest Income Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	$ (30)	$ 12	$ (107)	$ 3
Gain (Loss) on Hedged Items - Interest Income (Expense)	126	155	436	436
Interest Income Expense [Member] | Interest rate contracts/AFS securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	(33)	4	(117)	(18)
Gain (Loss) on Hedged Items - Interest Income (Expense)	141	187	482	506
Interest Income Expense [Member] | Interest rate contracts/commercial loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)		(6)		(17)
Interest Income Expense [Member] | Interest rate contracts/subordinated debt [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	3	14	10	38
Gain (Loss) on Hedged Items - Interest Income (Expense)	(15)	(32)	(46)	(70)
Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	(38)	(1,311)	(317)	(1,635)
Gain (Loss) on Hedged Items - Interest Income (Expense)	55	1,266	314	1,589
Other Income [Member] | Interest rate contracts/AFS securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	(41)	(1,322)	(326)	(1,640)
Gain (Loss) on Hedged Items - Interest Income (Expense)	58	1,278	323	1,598
Other Income [Member] | Interest rate contracts/commercial loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)		1		1
Gain (Loss) on Hedged Items - Interest Income (Expense)		(1)		(3)
Other Income [Member] | Interest rate contracts/subordinated debt [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	3	10	9	4
Gain (Loss) on Hedged Items - Interest Income (Expense)	$ (3)	$ (11)	$ (9)	$ (6)