Basis of Presentation - Schedule of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands			1 Months Ended
	Oct. 15, 2019	Mar. 01, 2019	Oct. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Purchase price:
Contingent consideration, at fair value				$ 0	$ 28,484
5 Arches, LLC
Purchase price:
Cash		$ 12,575
Contingent consideration, at fair value		24,621		$ 15,000
Purchase option, at fair value		5,082
Equity method investment, at fair value		8,052
Allocated to:
Business purpose loans, at fair value		2,022
Cash and cash equivalents		2,128
Restricted cash		9,082
Other assets		5,473
Goodwill		28,747
Intangible assets		24,800
Deferred tax asset		0
Total assets acquired		72,252
Asset-backed securities issued, at fair value		0
Short-term debt, net		3,800
Accrued expenses and other liabilities		13,920
Deferred tax liability		4,202
Total liabilities assumed		21,922
Total net assets acquired		$ 50,330
CoreVest LLC
Purchase price:
Cash	$ 482,311		$ 482,000
Contingent consideration, at fair value	0
Purchase option, at fair value	0
Equity method investment, at fair value	0
Allocated to:
Business purpose loans, at fair value	2,610,490
Cash and cash equivalents	30,685
Restricted cash	0
Other assets	67,420
Goodwill	59,928
Intangible assets	56,500
Deferred tax asset	2,577
Total assets acquired	2,827,600
Asset-backed securities issued, at fair value	1,656,023
Short-term debt, net	663,275
Accrued expenses and other liabilities	25,991
Deferred tax liability	0
Total liabilities assumed	2,345,289
Total net assets acquired	$ 482,311