Borrowings - Assets Sold Under Agreement to Repurchase (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Apr. 01, 2020	Dec. 31, 2019
During the period:
Total interest expense	$ 27,322,000	$ 19,429,000	$ 70,493,000	$ 47,709,000
Carrying value:
Unpaid principal balance	7,267,046,000		7,267,046,000			$ 4,141,680,000
Unamortized debt issuance costs and premiums	(7,858,000)		(7,858,000)			(627,000)
Unamortized debt issuance costs	(7,858,000)		(7,858,000)			(627,000)
Total loans sold under agreements to repurchase	$ 7,259,188,000		$ 7,259,188,000			$ 4,141,053,000
Weighted average interest rate (as a percent)	1.85%		1.85%			3.29%
Available borrowing capacity committed	$ 17,072,000		$ 17,072,000			$ 125,810,000
Available borrowing capacity uncommitted	2,940,882,000		2,940,882,000			782,510,000
Available borrowing capacity	2,957,954,000		2,957,954,000			908,320,000
Servicing advances	232,519,000		232,519,000			207,460,000
Margin deposits placed with counterparties	4,375,000		4,375,000			5,000,000
Loans held for sale
Carrying value:
Fair value of assets pledged to secure	8,453,522,000		8,453,522,000			4,322,789,000
Mortgage servicing rights
Carrying value:
Fair value of assets pledged to secure	2,283,876,000		2,283,876,000			2,902,721,000
Servicing advances
Carrying value:
Fair value of assets pledged to secure	232,519,000		232,519,000			207,460,000
Financing receivable
Carrying value:
Fair value of assets pledged to secure	86,958,000		86,958,000			$ 107,512,000
Deposits
Carrying value:
Fair value of assets pledged to secure	192,597,000		192,597,000
Note Payable
During the period:
Average balance of assets sold under agreements to repurchase	1,300,000,000	1,300,000,000	1,300,000,000	1,300,000,000
Carrying value:
Amortization of debt issuance costs	459,000	445,000	1,400,000	1,300,000
Assets sold under agreements to repurchase
During the period:
Average balance of assets sold under agreements to repurchase	$ 3,363,140,000	$ 2,098,208,000	$ 2,669,336,000	$ 1,861,086,000
Weighted-average interest rate (as a percent)	2.68%	3.66%	3.06%	4.08%
Total interest expense	$ 27,322,000	$ 19,429,000	$ 70,493,000	$ 47,709,000
Maximum daily amount outstanding	7,267,046,000	3,539,459,000	7,267,046,000	3,539,459,000
Carrying value:
Amortization of debt issuance costs	$ 4,800,000		$ 9,200,000
Amortization of premium		200,000		9,200,000
Amount of Master Repurchase Agreement incentives to refinance include in interest expense		$ 1,600,000		$ 14,700,000
PLS | Credit Suisse First Boston Mortgage Capital LLC | Note Payable
Mortgage loans sold under agreement to repurchase
Maximum loan amount					$ 600,000,000