Receivables Held for Sale - Summary of Components of Cumulative Lower of Amortized Cost or Fair Value Adjustment (Detail) - USD ($)		3 Months Ended			6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015		Jun. 30, 2016		Jun. 30, 2015
Lower of amortized cost or fair value adjustment recorded as a component of:
Initial lower of amortized cost or fair value adjustment		$ 8,000,000			$ 25,000,000		$ 220,000,000
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		62,000,000	$ 274,000,000		130,000,000		291,000,000
Fair Value [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		70,000,000	273,000,000		155,000,000		273,000,000
Settlement (Including Short Sales) [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		(8,000,000)	1,000,000		(25,000,000)		18,000,000
Provision for Credit Losses [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Initial lower of amortized cost or fair value adjustment	[1]	6,000,000	220,000,000		19,000,000		220,000,000
Provision for Credit Losses [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	[1]	6,000,000	220,000,000		19,000,000		220,000,000
Provision for Credit Losses [Member] | Settlement (Including 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	[1]	0	0		0		0
Other Revenue [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Initial lower of amortized cost or fair value adjustment		2,000,000	0	[2]	6,000,000	[2]	0	[2]
Subsequent to initial transfer to held for sale		54,000,000	54,000,000		105,000,000		71,000,000
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		56,000,000	54,000,000		111,000,000		71,000,000
Other Revenue [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		2,000,000	0	[2]	6,000,000	[2]	0	[2]
Subsequent to initial transfer to held for sale		62,000,000	53,000,000		130,000,000		53,000,000
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		64,000,000	53,000,000		136,000,000		53,000,000
Other Revenue [Member] | Settlement (Including 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	[2]	0	0		0		0
Subsequent to initial transfer to held for sale		(8,000,000)	1,000,000		(25,000,000)		18,000,000
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		$ (8,000,000)	$ 1,000,000		$ (25,000,000)		$ 18,000,000

[1] Represents the portion of the initial lower of amortized cost or fair value adjustment attributable to credit factors which was recorded as provision for credit losses in the consolidated statement of income (loss) as there was no objective, verifiable evidence to indicate non-credit factors were associated with the decline in fair value.

[2] Represents the portion of the initial lower of amortized cost or fair value adjustment attributable to non-credit factors which was recorded as a component of total other revenues in the consolidated statement income (loss) as it reflects the impact on value caused by current marketplace conditions including changes in interest rates.