Schedule III - Real Estate and Accumulated Depreciation (Details) - Reconciliation of Accumulated Depreciation - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance	$ 193,021	$ 134,311	$ 88,173
Depreciation expenses	72,725	63,872	49,619
Property assets fully depreciated and written off	(5,631)	(5,162)	(3,481)
Balance	$ 260,115	$ 193,021	$ 134,311