Derivative Financial Instruments - Gains and Losses on Hedged Items in Fair Value Hedges (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Interest Income Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	$ (52)	$ (60)
Gain (Loss) on Hedged Items - Interest Income (Expense)	98	164
Interest Income Expense [Member] | Interest rate contracts/AFS securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	(56)	(46)
Gain (Loss) on Hedged Items - Interest Income (Expense)	112	179
Interest Income Expense [Member] | Interest rate contracts/subordinated debt [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	4	(14)
Gain (Loss) on Hedged Items - Interest Income (Expense)	(14)	(15)
Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	169	302
Gain (Loss) on Hedged Items - Interest Income (Expense)	(173)	(291)
Other Income [Member] | Interest rate contracts/AFS securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	170	298
Gain (Loss) on Hedged Items - Interest Income (Expense)	(174)	(287)
Other Income [Member] | Interest rate contracts/subordinated debt [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative - Interest Income (Expense)	(1)	4
Gain (Loss) on Hedged Items - Interest Income (Expense)	$ 1	$ (4)