Payables and Other Liabilities - Repurchase Reserves (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Loans Subject to Repurchase Reserve [Roll Forward]
Balance - beginning of period	$ 16	$ 9	$ 8	$ 9
Provisions	8	2	16	3
Releases	(1)	(2)	(1)	(3)
Balance - end of period	$ 23	$ 9	$ 23	$ 9