Receivables Held for Sale - Summary of Components of Cumulative Lower of Amortized Cost or Fair Value Adjustment (Detail) - USD ($)		1 Months Ended	3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Lower of amortized cost or fair value adjustment recorded as a component of:
Initial lower of amortized cost or fair value adjustment		$ 541,000,000	$ 562,000,000	$ 12,000,000	$ 587,000,000	$ 232,000,000
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale			565,000,000	95,000,000	695,000,000	386,000,000
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			577,000,000	96,000,000	732,000,000	369,000,000
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			(12,000,000)	(1,000,000)	(37,000,000)	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	[1]		557,000,000	12,000,000	576,000,000	232,000,000
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]		557,000,000	12,000,000	576,000,000	232,000,000
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]		5,000,000	0	11,000,000	0
Subsequent to initial transfer to held for sale			3,000,000	83,000,000	108,000,000	154,000,000
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale			8,000,000	83,000,000	119,000,000	154,000,000
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]		5,000,000	0	11,000,000	0
Subsequent to initial transfer to held for sale			15,000,000	84,000,000	145,000,000	137,000,000
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale			20,000,000	84,000,000	156,000,000	137,000,000
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			(12,000,000)	(1,000,000)	(37,000,000)	17,000,000
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale			$ (12,000,000)	$ (1,000,000)	$ (37,000,000)	$ 17,000,000

[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).

[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.