Real Estate Securities, Available for Sale - Investments in CRE Securities (Details) $ in Thousands	Sep. 30, 2020 USD ($) security	Dec. 31, 2019 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 36,250	$ 252,824
Financing transaction, carrying value	2,556,443
Credit facilities
Debt Securities, Available-for-sale [Line Items]
Financing transaction, carrying value	608,632
Non-subordinated CMBS \| Credit facilities
Debt Securities, Available-for-sale [Line Items]
Financing transaction, carrying value	$ 18,400
Real estate securities, available for sale
Debt Securities, Available-for-sale [Line Items]
Count \| security	11	43
Principal Amount	$ 67,334	$ 292,284
Total Discount	(35,375)	(55,981)
Amortized Cost	31,959	236,303
Cumulative Unrealized Gain on Investments	4,291	17,084
Cumulative Unrealized (Loss) on Investments	0	(563)
Fair Value	$ 36,250	$ 252,824
Weighted Average, Coupon (in percentage)	3.47%	3.19%
Weighted Average, Unleveraged Current Yield (in percentage)	0.00%	7.12%

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