Short-Term Debt - Assets Sold Under Agreement to Repurchase (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Carrying value:
Unpaid principal balance	$ 5,441,126,000
Total loans sold under agreements to repurchase	5,435,354,000		$ 3,763,956,000
Loans held for sale	5,200,350,000		4,420,691,000
Servicing advances, net	$ 499,955,000		$ 694,038,000
Assets, Pledging Purpose [Extensible Enumeration]	Notes Payable		Notes Payable
Mortgage servicing rights, at fair value	$ 7,483,210,000		$ 7,099,348,000
Other Assets	623,368,000		582,460,000
Note Payable
During the period:
Average balance of assets sold under agreements to repurchase	1,950,330,000	$ 2,092,056,000
Carrying value:
Amortization of debt issuance costs	750,000	932,000
Loan Repo Facility
During the period:
Average balance of assets sold under agreements to repurchase	$ 3,542,537,000	$ 3,508,262,000
Weighted-average interest rate	7.24%	6.54%
Total interest expense	$ 70,435,000	$ 59,223,000
Maximum daily amount outstanding	5,442,438,000	5,768,570,000
Carrying value:
Unpaid principal balance	5,441,126,000		3,769,449,000
Unamortized debt issuance costs	(5,772,000)		(5,493,000)
Total loans sold under agreements to repurchase	$ 5,435,354,000		$ 3,763,956,000
Weighted average interest rate	6.92%		7.05%
Available borrowing capacity committed	$ 712,341,000		$ 1,282,040,000
Available borrowing capacity uncommitted	4,838,453,000		5,548,511,000
Available borrowing capacity	5,550,794,000		6,830,551,000
Amortization of debt issuance costs	6,700,000	$ 2,600,000
Asset Pledged as Collateral without Right
Carrying value:
Loans held for sale	5,127,134,000		4,329,501,000
Servicing advances, net	$ 271,947,000		$ 354,831,000
Assets, Pledging Purpose [Extensible Enumeration]	Notes Payable		Notes Payable
Mortgage servicing rights, at fair value	$ 7,406,892,000		$ 7,033,892,000
Other Assets	$ 16,175,000		$ 15,653,000
Asset Pledged as Collateral without Right | Mortgage servicing rights
Carrying value:
Assets, Pledging Purpose [Extensible Enumeration]	Notes Payable		Notes Payable
Asset Pledged as Collateral without Right | Note Payable | Mortgage servicing rights
Carrying value:
Mortgage servicing rights, at fair value	$ 7,406,892,000		$ 7,033,892,000
Asset Pledged as Collateral without Right | Note Payable | Servicing advances
Carrying value:
Servicing advances, net	271,947,000		354,831,000
Asset Pledged as Collateral without Right | Loan Repo Facility | Principal-only stripped MBS
Carrying value:
Principal-only stripped MBS	524,576,000
Asset Pledged as Collateral without Right | Loan Repo Facility | Mortgage servicing rights
Carrying value:
Mortgage servicing rights, at fair value	6,533,305,000		6,284,239,000
Asset Pledged as Collateral without Right | Loan Repo Facility | Servicing advances
Carrying value:
Servicing advances, net	271,947,000		354,831,000
Asset Pledged as Collateral without Right | Mortgage loans held for sale | Loan Repo Facility | Loans held for sale
Carrying value:
Loans held for sale	4,741,330,000		3,858,977,000
Asset Pledged as Collateral without Right | Deposits.
Carrying value:
Other Assets	16,175,000		15,653,000
Asset Pledged as Collateral without Right | Deposits. | Note Payable | Deposits
Carrying value:
Other Assets	16,175,000		15,653,000
Asset Pledged as Collateral without Right | Deposits. | Loan Repo Facility | Deposits
Carrying value:
Other Assets	$ 16,175,000		$ 15,653,000