Fair Value Measurements - Assets and Liabilities Recorded at Fair Value on Non-recurring Basis (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)		$ (18)	$ (588)	$ 149	$ (759)
Real estate secured receivables held for sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)		(16)	(565)	155	(695)
Receivables Held-for-Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)	[1]		(19)		(50)
Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Gains (Losses)	[2]	(2)	(4)	(6)	(14)
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale		0		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		0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale		275		275		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	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	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		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	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		10	812	10	812
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	757	0	757
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]		0		0
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]	10	55	10	55
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		256	9,391	256	9,391
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		256	9,391	256	9,391	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		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	0	0
Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total receivables held for sale		275		275		$ 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		266	10,203	266	10,203
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		256	10,148	256	10,148
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]		0		0
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]	$ 10	$ 55	$ 10	$ 55

[1] Total gains (losses) for the three and nine months ended September 30, 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.