Loans Held for Investment - Changes in Carrying Value of Securitized Loans Held For Investment Carried at Fair Value (Details) - Variable Interest Entities, Primary Beneficiary - Loans held for investment, at fair value - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Balance, beginning of period	$ 11,397,046	$ 11,359,236	$ 11,359,236
Purchases	0	1,421,537
Principal paydowns	(306,064)	(1,417,787)
Sales and settlements	(77,034)	(246)
Net periodic accretion (amortization)	(13,455)	(51,005)
Change in fair value	74,026	$ 85,311
Balance, end of period	$ 11,074,519		$ 11,397,046