Commitments and Contingencies - Repurchase and Foreclosure-Related Reserves (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Changes in repurchase and foreclosure-related reserves
Balance, beginning of period	$ 73	$ 89
Realized losses	(18)	(17)
Transfer of reserves	(7)	0
Increase in reserves due to:
Changes in assumptions	7	10
New loan sales	2	5
Balance, end of period	73	89	$ 57	$ 73	$ 87
Components of Repurchase and Foreclosure-related Reserves [Abstract]
Loan repurchase and indemnification liability			38	49
Adjustment to value for real estate owned			19	14
Allowance for probable foreclosure losses			0	10
Total	$ 73	$ 89	57	$ 73	$ 87
Loan Repurchases and Indemnifications
Loans with full risk of loss or with respect to which the company has identified a breach of representation and warranty provisions			$ 53
Percentage of loans with full risk of loss or with respect to which the company has identified a breach of representation and warranty provisions and are at least 90 days delinquent			23.00%
Recourse obligations
Loan Repurchases and Indemnifications
Estimated amount of reasonably possible losses in excess of the recorded liability			$ 10
LenderLive Network, LLC | Lease related guaranty
Off-Balance Sheet Arrangements and Guarantees
Amount of potential future lease payments under guarantee			$ 14