Receivables Held for Sale - Summary of Components of Cumulative Lower of Amortized Cost or Fair Value Adjustment (Detail) - USD ($)		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Lower of amortized cost or fair value adjustment recorded as a component of:
Initial lower of amortized cost or fair value adjustment(2)		$ 17,000,000	$ 0
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		68,000,000
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		85,000,000
Settlements, 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		(17,000,000)
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(2)	[1]	13,000,000
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(2)	[1]	13,000,000
Provision for Credit Losses [Member] | Settlements, 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)	[1]	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)	[2]	4,000,000
Subsequent to initial transfer to held for sale		51,000,000	17,000,000
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		55,000,000	17,000,000	[3]
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)	[2]	4,000,000
Subsequent to initial transfer to held for sale		68,000,000	0
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		72,000,000	0	[3]
Other Revenue [Member] | Settlements, 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)	[2]	0
Subsequent to initial transfer to held for sale		(17,000,000)	17,000,000
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		$ (17,000,000)	$ 17,000,000	[3]

[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.

[3] During the three months ended March 31, 2015, no lower of amortized cost or fair value adjustment was recorded as a provision for credit losses.