Receivables Held for Sale - Summary of Components of Cumulative Lower of Amortized Cost or Fair Value Adjustment (Detail) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014		Jun. 30, 2015	Jun. 30, 2014
Lower of amortized cost or fair value adjustment recorded as a component of:
Initial lower of amortized cost or fair value adjustment		$ 220	$ 42		$ (220)	$ 102
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		274			291
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		273			289
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 On Loans Held For Sale		0			0
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		1			2
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]	220			220
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]	220			220
Provision for Credit Losses [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	[1]	0			0
Provision for Credit Losses [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	[1]	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		0	42	[2]	0	102	[2]
Subsequent to initial transfer to held for sale		54	(139)		71	(310)
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		54	(97)	[3]	71	(208)	[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		0	42	[2]	0	102	[2]
Subsequent to initial transfer to held for sale		53	(137)		69	(313)
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		53	(95)	[3]	69	(211)	[3]
Other Revenue [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	[2]	0	0	[2]
Subsequent to initial transfer to held for sale		0	(2)		0	2
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		0	(2)	[3]	0	2	[3]
Other Revenue [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	[2]	0	0	[2]
Subsequent to initial transfer to held for sale		1	0		2	1
Lower Of Amortized Cost Or Fair Value Adjustment On Loans Held For Sale		$ 1	$ 0	[3]	$ 2	$ 1	[3]

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

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

[3] During three and six months ended June 30, 2014, no initial lower of amortized cost or fair value adjustment was attributed to credit factors and recorded as a provision for credit losses. The entire adjustment was attributable to non-credit related factors as these receivables were already carried at the lower of amortized cost or fair value of the collateral less cost to sell.