Summary of Significant Accounting Policies - Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Increase in minimum rent due to straight-line rent adjustment	$ 8,597	$ 5,237	$ 7,192
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	5.00%