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	Nationstar Mortgage Holdings Inc.	Nationstar Mortgage Holdings Inc. Common Stock	Nationstar Mortgage Holdings Inc. Additional Paid-in Capital	Nationstar Mortgage Holdings Inc. Retained Earnings	Nationstar Mortgage Holdings Inc. Treasury Share Amount	Nationstar Mortgage Holdings Inc. Total Nationstar Stockholders’ Equity and Mr. Cooper Stockholders’ Equity, respectively	Nationstar Mortgage Holdings Inc. Non-controlling Interests
Beginning of Period, shares at Dec. 31, 2017										97,728
Beginning of Period 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										450
Shares issued / (surrendered) under incentive compensation plan									(9)		(6)		(3)	(9)
Share-based compensation									17		17			17
Dividends to non-controlling interests									(1)		5			5	(6)
Net income (loss)									154			154		154
Ending of Period at Jul. 31, 2018	$ 1,056	$ 0	$ 1	$ 1,091	$ (36)	$ 0	$ 1,056	$ 0	1,883	$ 1	1,147	885	(151)	1,882	1
Ending of Period, shares at Jul. 31, 2018		1,000	90,806							98,178
Beginning of Period, shares at Jun. 30, 2018										98,163
Beginning of Period at Jun. 30, 2018									1,941	$ 1	1,140	949	(150)	1,940	1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan, shares										15
Shares issued / (surrendered) under incentive compensation plan									(3)		(2)		(1)	(3)
Share-based compensation									9		9			9
Net income (loss)									(64)			(64)		(64)
Ending of Period at Jul. 31, 2018	1,056	$ 0	$ 1	1,091	(36)	0	1,056	0	$ 1,883	$ 1	$ 1,147	$ 885	$ (151)	$ 1,882	$ 1
Ending of Period, shares at Jul. 31, 2018		1,000	90,806							98,178
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan, shares			5
Share-based compensation	2			2			2
Net income (loss)	1,020				1,020		1,020
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
Beginning of Period, shares at Dec. 31, 2018		1,000	90,821
Beginning of Period at Dec. 31, 2018	1,945	$ 0	$ 1	1,093	848	0	1,942	3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan, shares			266
Shares issued / (surrendered) under incentive compensation plan	(1)			(1)			(1)
Share-based compensation	14			14			14
Net income (loss)	(191)				(189)		(189)	(2)
Ending of Period at Sep. 30, 2019	1,767	$ 0	$ 1	1,106	659	0	1,766	1
Ending of Period, shares at Sep. 30, 2019		1,000	91,087
Beginning of Period, shares at Jun. 30, 2019		1,000	91,061
Beginning of Period at Jun. 30, 2019	1,678	$ 0	$ 1	1,100	575	0	1,676	2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan, shares			26
Shares issued / (surrendered) under incentive compensation plan	1			1			1
Share-based compensation	5			5			5
Net income (loss)	83				84		84	(1)
Ending of Period at Sep. 30, 2019	$ 1,767	$ 0	$ 1	$ 1,106	$ 659	$ 0	$ 1,766	$ 1
Ending of Period, shares at Sep. 30, 2019		1,000	91,087