Payables and Accrued Liabilities - Repurchase Reserves (Details) - USD ($) $ in Millions	5 Months Ended	7 Months Ended	12 Months Ended
	Dec. 31, 2018	Jul. 31, 2018	Dec. 31, 2017
Loans Subject to Repurchase Reserve [Roll Forward]
Repurchase Reserve	$ 9
Provisions	3
Releases	(4)
Charge-offs	0
Repurchase Reserve	8	$ 9
Predecessor
Loans Subject to Repurchase Reserve [Roll Forward]
Repurchase Reserve	$ 9	9	$ 18
Provisions		3	7
Releases		(3)	(14)
Charge-offs		0	(2)
Repurchase Reserve		$ 9	$ 9