Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Shares Amount	Total Nationstar Stockholders’ Equity and Mr. Cooper Stockholders’ Equity, respectively	Non-controlling Interests
Balance, shares (shares) (Predecessor) at Dec. 31, 2015			108,000
Balance (Predecessor) at Dec. 31, 2015	$ 1,767		$ 1	$ 1,105	$ 682	$ (30)	$ 1,758	$ 9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in shares) | Predecessor			86
Shares issued / (surrendered) under incentive compensation plan | Predecessor	(3)			0		(3)	(3)
Share-based compensation | Predecessor	21			21			21
Excess tax deficiency from share-based compensation | Predecessor	(4)			(4)			(4)
Repurchase of common stock (in shares) | Predecessor			(10,589)
Repurchase of common stock | Predecessor	(114)					(114)	(114)
Net income | Predecessor	16				19		19	(3)
Balance (Predecessor) at Dec. 31, 2016	1,683		$ 1	1,122	701	(147)	1,677	6
Balance, shares (shares) (Predecessor) at Dec. 31, 2016			97,497
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in shares) | Predecessor			231
Shares issued / (surrendered) under incentive compensation plan | Predecessor	(4)			(3)		(1)	(4)
Share-based compensation | Predecessor	17			17			17
Dividends to non-controlling interests | Predecessor	(5)			(5)			(5)
Net income | Predecessor	31				30		30	1
Balance (Predecessor) at Dec. 31, 2017	1,722		$ 1	1,131	731	(148)	1,715	7
Balance, shares (shares) (Predecessor) at Dec. 31, 2017			97,728
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in shares) | Predecessor			450
Shares issued / (surrendered) under incentive compensation plan | Predecessor	(9)			(6)		(3)	(9)
Share-based compensation | Predecessor	17			17			17
Dividends to non-controlling interests | Predecessor	(1)			5			5	(6)
Net income | Predecessor	154				154		154
Balance (Predecessor) at Jul. 31, 2018	1,883		$ 1	1,147	885	(151)	1,882	1
Balance at Jul. 31, 2018	1,056	$ 0	$ 1	1,091	(36)	0	1,056	0
Balance, shares (shares) (Predecessor) at Jul. 31, 2018			98,178
Balance, shares (shares) at Jul. 31, 2018		1,000	90,806
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Non-controlling interests acquired	3							3
Shares issued / (surrendered) under incentive compensation plan (in shares)			15
Share-based compensation	2			2			2
Net income	884				884		884
Balance at Dec. 31, 2018	$ 1,945	$ 0	$ 1	$ 1,093	$ 848	$ 0	$ 1,942	$ 3
Balance, shares (shares) at Dec. 31, 2018		1,000	90,821