Quarterly Financial Data (Unaudited) - Results (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended							5 Months Ended	7 Months Ended	12 Months Ended
	Jul. 31, 2018	Sep. 30, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018	Jul. 31, 2018	Dec. 31, 2019	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Service related, net	$ 120	$ 259	$ 430	$ 258	$ 137	$ 84	$ 159	$ 317	$ 464	$ 418	$ 901	$ 909	$ 1,043
Net gain on mortgage loans held for sale	44	83	310	360	262	166	93	127	124	176	295	1,098	607
Total revenues	164	342	740	618	399	250	252	444	588	594	1,196	2,007	1,650
Total expenses	242	275	438	478	492	443	432	339	364	707	945	1,851	1,475
Total other income (expenses), net	(5)	(26)	(62)	(33)	(24)	(40)	2	(26)	(18)	(24)	(49)	(159)	(131)
Income (loss) before income tax expense (benefit)	(83)	41	240	107	(117)	(233)	(178)	79	206	(137)	202	(3)	44
Less: Income tax expense (benefit)	(19)	(979)	(221)	24	(29)	(47)	(42)	21	46	(1,021)	48	(273)	13
Net income (loss)	(64)	1,020	461	83	(88)	(186)	(136)	58	160	884	154	270	31
Net (loss) income attributable to non-controlling interests	0	0	(2)	(1)	(1)	0	0	0	0	0	0	(4)	1
Net income	(64)	1,020	463	84	(87)	(186)	(136)	58	160	884	154	274	30
Less: Undistributed earnings attributable to participating stockholders	0	9	4	1	0	0	0	0	0	8	0	2	0
Net income attributable to common stockholders	$ (64)	$ 1,011	$ 459	$ 83	$ (87)	$ (186)	$ (136)	$ 58	$ 160	$ 876	$ 154	$ 272	$ 30
Net income (loss) per common share attributable to Predecessor/Successor:
Basic (in dollars per share)	$ (0.65)	$ 11.13	$ 5.03	$ 0.91	$ (0.96)	$ (2.05)	$ (1.50)	$ 0.59	$ 1.63	$ 9.65	$ 1.57	$ 2.99	$ 0.31
Diluted (in dollars per share)	$ (0.65)	$ 10.99	$ 4.95	$ 0.90	$ (0.96)	$ (2.05)	$ (1.50)	$ 0.59	$ 1.61	$ 9.54	$ 1.55	$ 2.95	$ 0.30