Fair Value Measurements - Assets and Liabilities Recorded at Fair Value on Non-recurring Basis (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)		$ 111	$ (99)
Real estate secured receivables held for sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)		113	(68)
Receivables Held-for-Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)	[1]		(26)
Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)	[2]	(2)	(5)
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		0		0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale		1,921		6,129
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 receivables held for sale [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	[1]		0
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	[2]	0	0
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		26	1,653
Non-Recurring Fair Value Measurements [Member] | Level 2 [Member] | Real estate secured receivables held for sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale		0	1,299
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	[1]		274
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	[2]	26	80
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		1,911	6,886
Non-Recurring Fair Value Measurements [Member] | Level 3 [Member] | Real estate secured receivables held for sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale		1,911	6,886	5,674
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	[1]		0
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	[2]	0	0
Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale		1,921		$ 6,129
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		1,937	8,539
Total [Member] | Non-Recurring Fair Value Measurements [Member] | Real estate secured receivables held for sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale		1,911	8,185
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	[1]		274
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	[2]	26	80
Real Estate Secured Receivables Held for Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets transferred from Level 3 to Level 2		$ 3,665	$ 1,299

[1] Total gains (losses) for the three months ended March 31, 2016 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.