Borrowings - Note Payable (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Nov. 01, 2018	Feb. 01, 2018
During the period:
Total interest expense	$ 11,581,000	$ 18,039,000	$ 26,930,000	$ 36,034,000
Carrying value:
Notes payable	1,294,949,000		1,294,949,000		$ 1,294,070,000
Unused amount	2,090,894,000		2,090,894,000		908,320,000
Notes payable
Maximum loan amount	1,300,000,000		1,300,000,000
Note Payable
During the period:
Average balance	$ 1,300,000,000	$ 1,300,000,000	$ 1,300,000,000	$ 1,300,000,000
Weighted-average interest rate (as a percent)	3.28%	5.27%	3.86%	5.26%
Total interest expense	$ 11,109,000	$ 17,564,000	$ 25,955,000	$ 35,074,000
Maximum daily amount outstanding	1,300,000,000	1,300,000,000	1,300,000,000	1,300,000,000
Carrying value:
Unpaid principal balance	1,300,000,000		1,300,000,000		1,300,000,000
Unamortized debt issuance costs	(5,051,000)		(5,051,000)		(5,930,000)
Notes payable	$ 1,294,949,000		$ 1,294,949,000		$ 1,294,070,000
Weighted-average interest rate (as a percent)	2.92%		2.92%		4.46%
Amortization of Financing Costs	$ 451,000	$ 445,000	$ 896,000	$ 889,000
Note Payable | Revolving credit agreement
Short-term debt
Maximum loan amount						$ 150,000,000
Notes payable
Increase in loan amount			0		$ 0
Note Payable | Credit Suisse AG
Short-term debt
Maximum loan amount							$ 400,000,000
Note Payable | Mortgage servicing rights
Carrying value:
Assets pledged to secure	2,129,361,000		2,129,361,000		2,861,442,000
Notes payable
Increase in loan amount			0		0
Note Payable | Servicing advances
Carrying value:
Assets pledged to secure	197,094,000		197,094,000		$ 207,460,000
Note Payable | Deposits
Carrying value:
Assets pledged to secure	125,017,000		$ 125,017,000
Notes Payable Term Loan 2018-GT1
Notes payable
Debt instrument option to extend period			2 years
Notes Payable Term Loan 2018-GT1 | LIBOR
Notes payable
Maximum loan amount	650,000,000		$ 650,000,000
Interest rate spread			2.85%
Notes Payable Term Loan 2018-GT2
Notes payable
Debt instrument option to extend period			2 years
Notes Payable Term Loan 2018-GT2 | LIBOR
Notes payable
Maximum loan amount	$ 650,000,000		$ 650,000,000
Interest rate spread			2.65%