Long-Term Debt - Note Payable (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
During the period:
Unpaid principal balance	$ 3,490,082,000		$ 3,490,082,000
Carrying value:
Notes payable	1,793,972,000		1,793,972,000		$ 1,297,622,000
Unsecured senior notes	1,778,988,000		1,778,988,000		1,776,219,000
Note Payable
During the period:
Average balance	$ 1,800,000,000	$ 1,300,000,000	$ 1,510,623,000	$ 1,300,000,000
Weighted-average interest rate (as a percent)	5.31%	2.87%	4.13%	2.89%
Total interest expense	$ 24,795,000	$ 9,896,000	$ 48,360,000	$ 29,888,000
Carrying value:
Unpaid principal balance	1,800,000,000		1,800,000,000		1,300,000,000
Unamortized debt issuance costs	(6,028,000)		(6,028,000)		(2,378,000)
Notes payable	$ 1,793,972,000		$ 1,793,972,000		$ 1,297,622,000
Weighted-average interest rate (as a percent)	6.12%		6.12%		2.84%
Amortization of Financing Costs	$ 726,000	570,000	$ 1,700,000	1,700,000
Notes payable
Maximum loan amount	1,800,000,000		$ 1,800,000,000
Debt instrument option to extend period			2 years
Note Payable | Mortgage servicing rights
Carrying value:
Assets pledged to secure	5,089,648,000		$ 5,089,648,000		$ 3,856,791,000
Note Payable | Servicing advances
Carrying value:
Assets pledged to secure	253,370,000		253,370,000		232,107,000
Note Payable | Deposits
Carrying value:
Assets pledged to secure	9,886,000		$ 9,886,000		36,632,000
Notes Payable Term Loan 2018-GT1
Notes payable
Debt instrument option to extend period			2 years
Notes Payable Term Loan 2018-GT1 | SOFR
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 | SOFR
Notes payable
Maximum loan amount	650,000,000		$ 650,000,000
Interest rate spread			2.65%
Notes Payable Term Loan 2022-GT1 | SOFR
Long-Term debt
Maximum loan amount	500,000,000		$ 500,000,000
Notes payable
Interest rate spread			4.25%
Unsecured Senior Note
During the period:
Average balance	$ 1,800,000,000	$ 1,381,522,000	$ 1,800,000,000	$ 1,229,853,000
Weighted-average interest rate (as a percent)	5.07%	4.91%	5.07%	4.86%
Total interest expense	$ 23,949,000	$ 17,442,000	$ 71,065,000	$ 46,281,000
Unpaid principal balance	1,800,000,000		1,800,000,000		1,800,000,000
Unamortized debt issuance costs and premiums	(21,012,000)		(21,012,000)		(23,781,000)
Debt Instrument Unamortized Premium And Debt Issuance Costs Net	$ 1,778,988,000		$ 1,778,988,000		$ 1,776,219,000
Weighted average interest rate (as a percent)	5.07%		5.07%		5.07%
Carrying value:
Amortization of Financing Costs	$ 933,000	$ 492,000	$ 2,800,000	$ 1,400,000
Notes payable
Maximum loan amount	1,800,000,000		$ 1,800,000,000
Redemption rate (as a percent)			100.00%
Unsecured Senior Note | Before October 15, 2022 with up to 40% principal redeemed
Notes payable
Redemption rate (as a percent)			40.00%
Unsecured Senior Notes One Due October 2025
Notes payable
Maximum loan amount	500,000,000		$ 500,000,000
Interest rate spread			5.38%
Unsecured Senior Notes Two Due October 2025
Notes payable
Maximum loan amount	150,000,000		$ 150,000,000
Interest rate spread			5.38%
Unsecured Senior Notes Due February 2029
Notes payable
Maximum loan amount	650,000,000		$ 650,000,000
Interest rate spread			4.25%
Unsecured Senior Notes Due September 2031
Notes payable
Maximum loan amount	$ 500,000,000		$ 500,000,000
Interest rate spread			5.75%