Quarterly Financial Data (Unaudited) (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, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Jul. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Service related, net		$ 259	$ 159							$ 418
Net gain on mortgage loans held for sale		83	93							176
Total revenues		342	252							594
Total expenses		275	432							707
Total other income (expenses), net		(26)	2							(24)
Income (loss) before income tax expense (benefit)		41	(178)							(137)
Less: Income tax expense (benefit)		(979)	(42)							(1,021)
Net income (loss)		1,020	(136)							884
Net income (loss) attributable to non-controlling interests		0	0							0
Net income attributable to Successor/Predecessor		1,020	(136)							884
Less: Undistributed earnings attributable to participating stockholders		9	0							8
Net income attributable to common stockholders		$ 1,011	$ (136)							$ 876
Net income (loss) per common share attributable to Predecessor/Successor:
Basic (in dollars per share)		$ 11.13	$ (1.50)							$ 9.65
Diluted (in dollars per share)		$ 10.99	$ (1.50)							$ 9.54
Predecessor
Service related, net	$ 120			$ 317	$ 464	$ 295	$ 252	$ 213	$ 283		$ 901	$ 1,043	$ 1,122
Net gain on mortgage loans held for sale	44			127	124	142	154	167	144		295	607	793
Total revenues	164			444	588	437	406	380	427		1,196	1,650	1,915
Total expenses	242			339	364	366	368	369	372		945	1,475	1,644
Total other income (expenses), net	(5)			(26)	(18)	(13)	(26)	(40)	(52)		(49)	(131)	(242)
Income (loss) before income tax expense (benefit)	(83)			79	206	58	12	(29)	3		202	44	29
Less: Income tax expense (benefit)	(19)			21	46	17	5	(10)	1		48	13	13
Net income (loss)	(64)			58	160	41	7	(19)	2		154	31	16
Net income (loss) attributable to non-controlling interests	0			0	0	0	0	1	0		0	1	(3)
Net income attributable to Successor/Predecessor	(64)			58	160	$ 41	$ 7	$ (20)	$ 2		154	30	19
Less: Undistributed earnings attributable to participating stockholders	0			0	0						0	0	0
Net income attributable to common stockholders	$ (64)			$ 58	$ 160						$ 154	$ 30	$ 19
Net income (loss) per common share attributable to Predecessor/Successor:
Basic (in dollars per share)	$ (0.65)			$ 0.59	$ 1.63	$ 0.42	$ 0.07	$ (0.20)	$ 0.02		$ 1.57	$ 0.31	$ 0.19
Diluted (in dollars per share)	$ (0.65)			$ 0.59	$ 1.61	$ 0.41	$ 0.07	$ (0.20)	$ 0.02		$ 1.55	$ 0.30	$ 0.19