Fair Value Measurements - Assets and Liabilities Recorded at Fair Value on Non-recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)	$ (93)		$ (72)
Real Estate Secured [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)	(17)		111
Receivables Held-for-Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)	(72)	[1]	(163)	[1]
Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)	(4)	[2]	(20)	[2]
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale	0				0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale	352				0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale	819				937
Non-Recurring Fair Value Measurements [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	0		0
Non-Recurring Fair Value Measurements [Member] | Level 1 [Member] | Real Estate Secured [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale	0		0
Non-Recurring Fair Value Measurements [Member] | Level 1 [Member] | Receivables Held-for-Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables held for investment	0	[1]	0	[1]
Non-Recurring Fair Value Measurements [Member] | Level 1 [Member] | Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned	0	[2]	0	[2]
Non-Recurring Fair Value Measurements [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	1,048		2,117
Non-Recurring Fair Value Measurements [Member] | Level 2 [Member] | Real Estate Secured [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale	333		902
Non-Recurring Fair Value Measurements [Member] | Level 2 [Member] | Receivables Held-for-Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables held for investment	529	[1]	927	[1]
Non-Recurring Fair Value Measurements [Member] | Level 2 [Member] | Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned	186	[2]	288	[2]
Non-Recurring Fair Value Measurements [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	764		1,518
Non-Recurring Fair Value Measurements [Member] | Level 3 [Member] | Real Estate Secured [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale	764		1,518		860
Non-Recurring Fair Value Measurements [Member] | Level 3 [Member] | Receivables Held-for-Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables held for investment	0	[1]	0	[1]
Non-Recurring Fair Value Measurements [Member] | Level 3 [Member] | Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned	0	[2]	0	[2]
Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale	1,171				937
Total [Member] | Non-Recurring Fair Value Measurements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	1,812		3,635
Total [Member] | Non-Recurring Fair Value Measurements [Member] | Real Estate Secured [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale	1,097		2,420
Total [Member] | Non-Recurring Fair Value Measurements [Member] | Receivables Held-for-Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables held for investment	529	[1]	927	[1]
Total [Member] | Non-Recurring Fair Value Measurements [Member] | Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned	$ 186	[2]	$ 288	[2]

[1] Total gains (losses) for the three months ended March 31, 2015 and 2014 include amounts recorded on receivables that were subsequently transferred to held for sale.

[2] Real estate owned is required to be reported on the balance sheet net of transactions costs. The real estate owned amounts in the table above reflect the fair value of the underlying asset unadjusted for transaction costs.