Organization and Business - Schedule of Issuance and Sale of Common Stock (Details) - 2016 ATM Program - ATM Program - Operating Partnership - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common shares sold (in shares)	144,562	114,203	0	311,786	2,197,914	0	4,150,000	0	570,551	6,347,914
Weighted average price (in dollars per share)	$ 17.03	$ 17.15	$ 0	$ 17.85	$ 18.39	$ 0	$ 20.07	$ 0	$ 17.50	$ 19.48
Net proceeds	$ 2,442	$ 1,947	$ 0	$ 5,509	$ 40,011	$ 0	$ 82,440	$ 0	$ 9,898	$ 122,451