Payables and Accrued Liabilities - Repurchase Reserves (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended	7 Months Ended	9 Months Ended
	Jul. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Jul. 31, 2018	Sep. 30, 2017
Loans Subject to Repurchase Reserve [Roll Forward]
Balance - beginning of period		$ 9
Provisions		1
Releases		(1)
Charge-offs		0
Balance - end of period	$ 9	9		$ 9
Predecessor
Loans Subject to Repurchase Reserve [Roll Forward]
Balance - beginning of period	9	$ 9	$ 14	9	$ 18
Provisions	0		2	3	5
Releases	0		0	(3)	(6)
Charge-offs	0		(1)	0	(2)
Balance - end of period	$ 9		$ 15	$ 9	$ 15