Summary of Significant Accounting Policies - Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Increase in minimum rent due to straight-line rent adjustment	$ 11,755	$ 8,597	$ 5,237
Minimum
Revenues
Management fees as a percentage of gross monthly rental revenue	1.50%
Maximum
Revenues
Management fees as a percentage of gross monthly rental revenue	4.00%