Long-Term Debt - Note Payable (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
During the period:
Unpaid principal balance	$ 2,446,014,000		$ 2,446,014,000
Carrying value:
Notes payable	1,793,260,000		1,793,260,000		$ 1,297,622,000
Unsecured senior notes	1,778,055,000		1,778,055,000		1,776,219,000
Note Payable
During the period:
Average balance	$ 1,426,373,000	$ 1,300,000,000	$ 1,363,536,000	$ 1,300,000,000
Weighted-average interest rate (as a percent)	3.69%	2.91%	3.34%	2.90%
Total interest expense	$ 13,656,000	$ 10,104,000	$ 23,565,000	$ 19,992,000
Carrying value:
Unpaid principal balance	1,800,000,000		1,800,000,000		1,300,000,000
Unamortized debt issuance costs	(6,740,000)		(6,740,000)		(2,378,000)
Notes payable	$ 1,793,260,000		$ 1,793,260,000		$ 1,297,622,000
Weighted-average interest rate (as a percent)	4.76%		4.76%		2.84%
Amortization of Financing Costs	$ 548,000	634,000	$ 1,000,000.0	1,200,000
Notes payable
Maximum loan amount	1,800,000,000		1,800,000,000
Note Payable | Mortgage servicing rights
Carrying value:
Assets pledged to secure	4,681,236,000		4,681,236,000		$ 3,856,791,000
Note Payable | Servicing advances
Carrying value:
Assets pledged to secure	279,664,000		279,664,000		232,107,000
Note Payable | Deposits
Carrying value:
Assets pledged to secure	25,547,000		$ 25,547,000		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	$ 1,300,000,000	$ 1,800,000,000	$ 1,152,762,000
Weighted-average interest rate (as a percent)	5.07%	4.81%	5.07%	4.81%
Total interest expense	$ 23,688,000	$ 16,169,000	$ 47,116,000	$ 28,839,000
Unpaid principal balance	1,800,000,000		1,800,000,000		1,800,000,000
Unamortized debt issuance costs and premiums	(21,945,000)		(21,945,000)		(23,781,000)
Debt Instrument Unamortized Premium And Debt Issuance Costs Net	$ 1,778,055,000		$ 1,778,055,000		$ 1,776,219,000
Weighted average interest rate (as a percent)	5.07%		5.07%		5.07%
Carrying value:
Amortization of Financing Costs	$ 923,000	$ 571,000	$ 1,800,000	$ 918,000
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%