Schedule III - Real Estate Investments (Summary of Historical Cost and Accumulated Depreciation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property
Balance, beginning of period	$ 1,177,582	$ 905,735	$ 734,828
Disposals	(5,617)	(54)
Additions (acquisitions and improvements)	411,188	271,901	170,907
Balance, end of period	1,583,153	1,177,582	905,735
Accumulated depreciation
Balance, beginning of period	(180,167)	(137,725)	(102,900)
Disposals	1,377	39
Additions (depreciation and amortization expense)	(61,146)	(42,481)	(34,825)
Balance, end of period	$ (239,936)	$ (180,167)	$ (137,725)