Earnings Per Share - Computation of Basic and Diluted Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income (loss) from continuing operations	$ 427	$ 77	$ 986	$ (82)
Less: Net loss attributable to non-controlling interests	0	0	0	(3)
Less: Undistributed earnings from continuing operations attributable to participating stockholders	4	1	9	0
Net income (loss) from continuing operations attributable to Mr. Cooper common stockholders	423	76	977	(79)
Net income (loss) from discontinued operations	12	(4)	14	(16)
Less: Undistributed earnings from discontinued operations attributable to participating stockholders	0	0	0	0
Net income (loss) from discontinued operations attributable to Mr. Cooper common stockholders	12	(4)	14	(16)
Net income	439	73	1,000	(98)
Less: Net loss attributable to non-controlling interests	0	0	0	(3)
Net income (loss) attributable to Mr. Cooper	439	73	1,000	(95)
Less: Undistributed earnings attributable to participating stockholders	4	1	9	0
Net income (loss) attributable to common stockholders	$ 435	$ 72	$ 991	$ (95)
Earnings Per Share, Basic [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share	$ 4.91	$ 0.82	$ 11.13	$ (0.86)
Income (Loss) from Continuing Operations, Per Diluted Share	4.72	0.81	10.65	(0.86)
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share	0.14	(0.04)	0.16	(0.18)
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share	0.13	(0.04)	0.15	(0.18)
Basic (in dollars per share)	5.05	0.78	11.29	(1.04)
Diluted (in dollars per share)	$ 4.85	$ 0.77	$ 10.80	$ (1.04)
Weighted average shares of common stock outstanding (in thousands):
Basic (in shares)	86,142	91,997	87,791	91,691
Dilutive effect of stock awards (in shares)	2,664	176	3,123	0
Dilutive effect of participating securities (in shares)	839	839	839	0
Diluted (in shares)	89,645	93,012	91,753	91,691