Investments in Real Estate - Investments in Existing Properties (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Real Estate Investments, Net [Abstract]
Capitalized costs on existing properties	$ 5,600	$ 6,800
Re-leasing costs	2,500	759
Recurring capital expenditures	147	365
Nonrecurring building improvements	$ 3,000	$ 5,700