Net Interest Income (Expense) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Interest income:
Interest income	$ 166,552,000	$ 82,994,000	$ 467,982,000	$ 186,740,000
Interest expense:
Obligations under capital lease				20,000
Interest expense	156,863,000	82,965,000	467,276,000	231,399,000
Net interest income (expense)	9,689,000	29,000	706,000	(44,659,000)
Nonrelated Party
Interest income:
Cash and short-term investments	15,814,000	7,759,000	53,186,000	8,736,000
Loans held for sale at fair value	65,641,000	38,945,000	205,414,000	124,835,000
Placement fees relating to custodial funds	85,076,000	36,290,000	209,319,000	53,169,000
Interest expense:
Assets sold under agreements to repurchase	62,758,000	24,329,000	209,461,000	67,048,000
Mortgage loan participation purchase and sale agreements	4,383,000	2,073,000	11,768,000	4,570,000
Notes payable	55,676,000	24,795,000	150,271,000	48,360,000
Unsecured senior notes	23,949,000	23,949,000	71,065,000	71,065,000
Obligations under capital lease				20,000
Interest shortfall on repayments of mortgage loans serviced for Agency securitizations	6,857,000	5,620,000	16,781,000	35,385,000
Interest on mortgage loan impound deposits	2,888,000	2,199,000	7,080,000	4,951,000
Other	352,000		850,000
Interest expense	156,863,000	82,965,000	467,276,000	231,399,000
Related Party | Townsgate Closing Services, LLC
Interest income:
Interest income	21,000		63,000
Loan Repo Facility
Interest expense:
Assets sold under agreements to repurchase	$ 62,758,000	$ 24,329,000	$ 209,461,000	$ 67,048,000