INVESTMENTS IN EXCESS MORTGAGE SERVICING RIGHTS ASSETS - Schedule of Activity Related to the Carrying Value of Investments in Excess MSRs (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($)
Carrying Value of Investments in Excess MSRs
Beginning balance	$ 5,686,233
Ending balance	5,021,086
Excess MSRs
Carrying Value of Investments in Excess MSRs
Beginning balance	379,747
Interest income	12,582
Other income	1,202
Proceeds from repayments	(35,924)
Proceeds from sales	(48)
Change in fair value	(11,109)
Ending balance	346,450
Excess MSRs | Mr. Cooper
Carrying Value of Investments in Excess MSRs
Beginning balance	377,692
Interest income	12,561
Other income	1,202
Proceeds from repayments	(35,708)
Proceeds from sales	(48)
Change in fair value	(11,184)
Ending balance	344,515
Excess MSRs | SLS
Carrying Value of Investments in Excess MSRs
Beginning balance	2,055
Interest income	21
Other income	0
Proceeds from repayments	(216)
Proceeds from sales	0
Change in fair value	75
Ending balance	$ 1,935