Unaudited Condensed 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	Treasury Share Amount	Total Mr. Cooper Stockholders’ Equity	Total Mr. Cooper Stockholders’ Equity Cumulative effect, period of adoption, adjustment	Non-controlling Interests
Shares outstanding, beginning balance (in shares) at Dec. 31, 2019			1,000	91,118
Stockholders' equity, beginning balance at Dec. 31, 2019	$ 2,231		$ 0	$ 1	$ 1,109	$ 1,122		$ 0	$ 2,232		$ (1)
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	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	$ 7	$ 0	$ 1	1,120	1,243	$ 7	(24)	2,340	$ 7	1
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		0	2,149		(4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in shares)				19
Shares issued / (surrendered) under incentive compensation plan	0				0				0
Share-based compensation	6				6				6
Repurchase of common stock (in shares)				(1,187)
Repurchase of common stock	(24)							(24)	(24)
Net income	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	$ 7	$ 0	$ 1	1,120	1,243	$ 7	(24)	2,340	$ 7	1
Shares outstanding, beginning balance (in shares) at Dec. 31, 2020			1,000	89,457
Stockholders' equity, beginning balance at Dec. 31, 2020	2,504		$ 0	$ 1	1,126	1,434		(58)	2,503		1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in shares)				1,242
Shares issued / (surrendered) under incentive compensation plan	(20)				(20)				(20)
Share-based compensation	21				21				21
Repurchase of common stock (in shares)				(15,578)
Repurchase of common stock	(516)							(516)	(516)
Stock Repurchased and Retired During Period, Shares			(1,000)
Stock Repurchased and Retired During Period, Value	(28)				(19)	(9)			(28)
Net income	1,299					1,299			1,299		0
Shares outstanding, ending balance (in shares) at Sep. 30, 2021			0	75,121
Stockholders' equity, ending balance at Sep. 30, 2021	3,260		$ 0	$ 1	1,108	2,724		(574)	3,259		1
Shares outstanding, beginning balance (in shares) at Jun. 30, 2021			1,000	86,149
Stockholders' equity, beginning balance at Jun. 30, 2021	3,350		$ 0	$ 1	1,120	2,434		(206)	3,349		1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in shares)				45
Shares issued / (surrendered) under incentive compensation plan	0				0				0
Share-based compensation	7				7				7
Repurchase of common stock (in shares)				(11,073)
Repurchase of common stock	(368)							(368)	(368)
Stock Repurchased and Retired During Period, Shares			(1,000)
Stock Repurchased and Retired During Period, Value	(28)				(19)	(9)			(28)
Net income	299					299			299		0
Shares outstanding, ending balance (in shares) at Sep. 30, 2021			0	75,121
Stockholders' equity, ending balance at Sep. 30, 2021	$ 3,260		$ 0	$ 1	$ 1,108	$ 2,724		$ (574)	$ 3,259		$ 1