Quarterly Results (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenue from tenants	$ 76,231	$ 72,863	$ 79,109	$ 71,541	$ 75,092	$ 74,888	$ 71,108	$ 70,119	$ 299,744	$ 291,207	$ 270,910
Net (loss) income attributable to common stockholders	$ (4,827)	$ (2,931)	$ 7,884	$ (3,227)	$ (13,524)	$ (27,245)	$ (12,041)	$ 15,401		$ (37,409)	$ (46,494)
Basic weighted-average shares outstanding (in shares)	107,286,620	106,139,668	106,075,741	106,076,588	106,096,401	105,905,281	105,028,459	105,196,387
Diluted weighted-average number of shares outstanding (in shares)	107,286,620	106,139,668	106,394,277	106,076,588	106,096,401	105,905,281	105,028,459	105,415,211
Basic and diluted net loss per share (in dollars per share)	$ (0.04)	$ (0.03)	$ 0.07	$ (0.03)	$ (0.13)	$ (0.26)	$ (0.11)	$ 0.15	$ (0.03)	$ (0.35)	$ (0.47)