Loans Held for Investment - Loan Portfolio Statistics (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan	Mar. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan	14	12
Total loan commitments	$ 296,050	$ 260,167
Principal balance	278,484	242,899	$ 272,234
Unamortized net deferred origination fees	(259)	(821)	(747)
Carrying value	$ 278,225	$ 242,078	$ 271,487
Weighted average coupon rate	5.70%	5.76%
Weighted average all in yield	6.39%	6.41%
Weighted average maximum maturity	3 years 1 month 6 days	3 years 7 months 6 days
Weighted average LTV (4)	0.68	0.70
Unfunded commitments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded loan commitments	$ 17,566	$ 17,268
Weighted average maximum maturity	1 year 6 months
First Mortgage Bridge Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value	$ 278,225	$ 242,078