Receivables Held for Sale - Summary of Components of Cumulative Lower of Amortized Cost or Fair Value Adjustment (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Lower of amortized cost or fair value adjustment recorded as a component of:
Lower of amortized cost or fair value adjustment	$ 314		$ 748		$ 18
Real Estate Owned [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Lower of amortized cost or fair value adjustment	(5)		40		50
Short Sales [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Lower of amortized cost or fair value adjustment	(3)		22		20
Other Income [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Initial lower of amortized cost or fair value adjustment	113		212		1,547
Subsequent to initial transfer to held for sale	(314)		(748)		(18)
Lower of amortized cost or fair value adjustment recorded through other revenues(1)	(201)	[1]	(536)	[1]	1,529
Lower of amortized cost or fair value adjustment					1,641
Other Income [Member] | Fair Value [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Initial lower of amortized cost or fair value adjustment	113		212		1,547
Subsequent to initial transfer to held for sale	(322)		(686)		52
Lower of amortized cost or fair value adjustment recorded through other revenues(1)	(209)	[1]	(474)	[1]	1,599
Lower of amortized cost or fair value adjustment					1,711
Other Income [Member] | Real Estate Owned [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Initial lower of amortized cost or fair value adjustment	0		0		0
Subsequent to initial transfer to held for sale	5		(40)		(50)
Lower of amortized cost or fair value adjustment recorded through other revenues(1)	5	[1]	(40)	[1]	(50)
Lower of amortized cost or fair value adjustment					(50)
Other Income [Member] | Short Sales [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Initial lower of amortized cost or fair value adjustment	0		0		0
Subsequent to initial transfer to held for sale	3		(22)		(20)
Lower of amortized cost or fair value adjustment recorded through other revenues(1)	3	[1]	(22)	[1]	(20)
Lower of amortized cost or fair value adjustment					(20)
Provision for Loan and Lease Losses [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Lower of amortized cost or fair value adjustment recorded as a provision for credit losses					112
Provision for Loan and Lease Losses [Member] | Fair Value [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Lower of amortized cost or fair value adjustment recorded as a provision for credit losses					112
Provision for Loan and Lease Losses [Member] | Real Estate Owned [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Lower of amortized cost or fair value adjustment recorded as a provision for credit losses					0
Provision for Loan and Lease Losses [Member] | Short Sales [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Lower of amortized cost or fair value adjustment recorded as a provision for credit losses					$ 0

[1] During 2014 and 2013, no lower of amortized cost or fair value adjustment was recorded as a provision for credit losses.