Unaudited Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Cumulative effect, period of adoption, adjustment	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative effect, period of adoption, adjustment	Total Mr. Cooper Stockholders’ Equity	Total Mr. Cooper Stockholders’ Equity Cumulative effect, period of adoption, adjustment	Non-controlling Interests	Treasury Stock
Shares outstanding, beginning balance (in shares) at Dec. 31, 2018			1,000	90,821
Stockholders' equity, beginning balance at Dec. 31, 2018	$ 1,945		$ 0	$ 1	$ 1,093	$ 848		$ 1,942		$ 3	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in 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)
Shares outstanding, ending balance (in shares) at Sep. 30, 2019			1,000	91,087
Stockholders' equity, ending balance at Sep. 30, 2019	1,767		$ 0	$ 1	1,106	659		1,766		1	0
Shares outstanding, beginning balance (in shares) at Dec. 31, 2018			1,000	90,821
Stockholders' equity, beginning balance at Dec. 31, 2018	1,945		$ 0	$ 1	1,093	848		1,942		3	0
Shares outstanding, ending balance (in shares) at Dec. 31, 2019			1,000	91,118
Stockholders' equity, ending balance at Dec. 31, 2019	$ 2,231	$ 7	$ 0	$ 1	1,109	1,122	$ 7	2,232	$ 7	(1)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting standards update	us-gaap:AccountingStandardsUpdate201613Member
Shares outstanding, beginning balance (in shares) at Jun. 30, 2019			1,000	91,061
Stockholders' equity, beginning balance at Jun. 30, 2019	$ 1,678		$ 0	$ 1	1,100	575		1,676		2	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in 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)
Shares outstanding, ending balance (in shares) at Sep. 30, 2019			1,000	91,087
Stockholders' equity, ending balance at Sep. 30, 2019	1,767		$ 0	$ 1	1,106	659		1,766		1	0
Shares outstanding, beginning balance (in shares) at Dec. 31, 2019			1,000	91,118
Stockholders' equity, beginning balance at Dec. 31, 2019	2,231	$ 7	$ 0	$ 1	1,109	1,122	$ 7	2,232	$ 7	(1)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in shares)				923
Shares issued / (surrendered) under incentive compensation plan	(5)				(5)			(5)
Share-based compensation	16				16			16
Repurchase of common stock (in shares)				(1,187)
Repurchase of common stock	(24)							(24)			(24)
Net income (loss)	116					114		114		2
Shares outstanding, ending balance (in shares) at Sep. 30, 2020			1,000	90,854
Stockholders' equity, ending balance at Sep. 30, 2020	$ 2,341		$ 0	$ 1	1,120	1,243		2,340		1	(24)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting standards update	us-gaap:AccountingStandardsUpdate201613Member
Shares outstanding, beginning balance (in shares) at Jun. 30, 2020			1,000	92,022
Stockholders' equity, beginning balance at Jun. 30, 2020	$ 2,145		$ 0	$ 1	1,114	1,034		2,149		(4)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in shares)				19
Share-based compensation	6				6			6
Repurchase of common stock (in shares)				(1,187)
Repurchase of common stock	(24)							(24)			(24)
Net income (loss)	214					209		209		5
Shares outstanding, ending balance (in shares) at Sep. 30, 2020			1,000	90,854
Stockholders' equity, ending balance at Sep. 30, 2020	$ 2,341		$ 0	$ 1	$ 1,120	$ 1,243		$ 2,340		$ 1	$ (24)