Unaudited Condensed 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 Mr. Cooper Stockholders’ Equity	Non-controlling Interests
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)		0	(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
Retirement of preferred stock	(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 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]
Repurchase of common stock (in shares)			14,800
Shares outstanding, ending balance (in shares) at Dec. 31, 2021		0	73,777
Stockholders' equity, ending balance at Dec. 31, 2021	3,367	$ 0	$ 1	1,116	2,879	(630)	3,366	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	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)
Retirement of preferred stock	(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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Repurchased and Retired During Period, Shares		1,000
Shares outstanding, ending balance (in shares) at Dec. 31, 2021		0	73,777
Stockholders' equity, ending balance at Dec. 31, 2021	3,367	$ 0	$ 1	1,116	2,879	(630)	3,366	1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in shares)			898
Shares issued / (surrendered) under incentive compensation plan	(22)			(41)		19	(22)
Share-based compensation	24			24			24
Dividends paid to noncontrolling interests	(1)							(1)
Repurchase of common stock (in shares)			(4,118)
Repurchase of common stock	(185)					(185)	(185)
Net income	922				922		922	0
Shares outstanding, ending balance (in shares) at Sep. 30, 2022		0	70,557
Stockholders' equity, ending balance at Sep. 30, 2022	4,105	$ 0	$ 1	1,099	3,801	(796)	4,105	0
Shares outstanding, beginning balance (in shares) at Jun. 30, 2022		0	71,651
Stockholders' equity, beginning balance at Jun. 30, 2022	4,037	$ 0	$ 1	1,094	3,688	(747)	4,036	1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued / (surrendered) under incentive compensation plan (in shares)			42
Shares issued / (surrendered) under incentive compensation plan	(1)			(2)		1	(1)
Share-based compensation	7			7			7
Dividends paid to noncontrolling interests	(1)							(1)
Repurchase of common stock (in shares)			(1,136)
Repurchase of common stock	(50)					(50)	(50)
Net income	113				113		113	0
Shares outstanding, ending balance (in shares) at Sep. 30, 2022		0	70,557
Stockholders' equity, ending balance at Sep. 30, 2022	$ 4,105	$ 0	$ 1	$ 1,099	$ 3,801	$ (796)	$ 4,105	$ 0