Advances - Schedule of Activity in Advances (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Advances [Roll Forward]
Beginning balance - before Allowance for Losses	$ 792,837	$ 1,032,180	$ 834,512	$ 1,066,448
Acquisition of advances in connection with the purchase of MSRs	4,495	0	4,495	0
New advances	180,317	225,483	383,717	469,028
Sales of advances	(115)	(226)	(248)	(454)
Collections of advances and other	(208,670)	(348,608)	(453,612)	(626,193)
Ending balance - before Allowance for Losses	768,864	908,829	768,864	908,829
Ending balance, net	$ 761,973	$ 901,009	$ 761,973	$ 901,009