Investment Activity - Schedule of Construction Mortgage Loans With Funding Commitments (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Mortgage Loans On Real Estate [Line Items]
Outstanding Balance	$ 42,773	$ 18,557
Sequel Construction Mortgage Loan
Mortgage Loans On Real Estate [Line Items]
Origination Date	2017-10
Total Commitment	$ 6,000
Outstanding Balance	$ 5,280
Haven Construction Mortgage Loan
Mortgage Loans On Real Estate [Line Items]
Origination Date	2018-01
Total Commitment	$ 19,000
Outstanding Balance	8,625
Sequel and Haven Construction Mortgage Loan
Mortgage Loans On Real Estate [Line Items]
Total Commitment	25,000
Outstanding Balance	$ 13,905