Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income (loss) attributable to Mr. Cooper	$ 209	$ 84	$ 114	$ (189)
Less: Undistributed earnings attributable to participating stockholders	2	1	1	0
Net income (loss) attributable to common stockholders	$ 207	$ 83	$ 113	$ (189)
Net income (loss) per common share attributable to Mr. Cooper:
Basic (in dollars per share)	$ 2.26	$ 0.91	$ 1.23	$ (2.08)
Diluted (in dollars per share)	$ 2.18	$ 0.90	$ 1.20	$ (2.08)
Weighted average shares of common stock outstanding (in thousands):
Basic (in shares)	91,682	91,080	91,688	91,012
Dilutive effect of stock awards (in shares)	2,563	117	1,529	0
Dilutive effect of participating securities (in shares)	839	839	839	0
Diluted (in shares)	95,084	92,036	94,056	91,012