Real Estate Securities - Unrealized Losses and Fair Value of Real Estate Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
CLOs
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Securities with an unrealized loss less than 12 months, Fair Value	$ 341,003	$ 315,845
Securities with an unrealized loss greater than 12 months, Fair Value	10,401	13,275
Securities with an unrealized loss less than 12 months, Unrealized Loss	(56,944)	(863)
Securities with an unrealized loss greater than 12 months, Unrealized Losses	(2,886)	(17)
SASB
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Securities with an unrealized loss less than 12 months, Fair Value	79,506	45,045
Securities with an unrealized loss greater than 12 months, Fair Value	10,250	12,151
Securities with an unrealized loss less than 12 months, Unrealized Loss	(7,468)	(67)
Securities with an unrealized loss greater than 12 months, Unrealized Losses	(1,287)	(31)
CMBS
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Securities with an unrealized loss less than 12 months, Fair Value	420,509	360,890
Securities with an unrealized loss greater than 12 months, Fair Value	20,651	25,426
Securities with an unrealized loss less than 12 months, Unrealized Loss	(64,412)	(930)
Securities with an unrealized loss greater than 12 months, Unrealized Losses	$ (4,173)	$ (48)