Unaudited Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Share Amount	Total Nationstar Stockholders' Equity and Mr. Cooper Stockholders' Equity, respectively	Non-controlling Interests
Beginning of Period, shares (Predecessor) at Dec. 31, 2016			97,497
Beginning of Period (Predecessor) at Dec. 31, 2016	$ 1,683		$ 1	$ 1,122	$ 701	$ (147)	$ 1,677	$ 6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan, shares | Predecessor			226
Shares issued / (surrendered) under incentive compensation plan | Predecessor	(4)			(3)		(1)	(4)
Share-based compensation | Predecessor	13			13			13
Dividends to non-controlling interests | Predecessor	(5)			(5)			(5)
Net income (loss) | Predecessor	(10)				(11)		(11)	1
Ending of Period (Predecessor) at Sep. 30, 2017	1,677		$ 1	1,127	690	(148)	1,670	7
Ending of Period, shares (Predecessor) at Sep. 30, 2017			97,723
Beginning of Period, shares (Predecessor) at Dec. 31, 2017			97,728
Beginning of Period (Predecessor) at Dec. 31, 2017	1,722		$ 1	1,131	731	(148)	1,715	7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan, 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 (loss) | Predecessor	154				154		154
Ending of Period (Predecessor) at Jul. 31, 2018	1,883		$ 1	1,147	885	(151)	1,882	1
Ending of Period at Jul. 31, 2018	1,056	$ 0	$ 1	1,091	(36)	0	1,056	0
Ending of Period, shares (Predecessor) at Jul. 31, 2018			98,178
Ending of Period, shares at Jul. 31, 2018		1,000	90,806
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan, shares			5
Shares issued / (surrendered) under incentive compensation plan	0					0	0
Share-based compensation	2			2			2
Net income (loss)	1,020				1,020		1,020	0
Ending of Period at Sep. 30, 2018	$ 2,078	$ 0	$ 1	$ 1,093	$ 984	$ 0	$ 2,078	$ 0
Ending of Period, shares at Sep. 30, 2018		1,000	90,811