Schedule III - Real Estate and Accumulated Depreciation - Changes in Real Estate Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
SCHEDULE III - REAL ESTATE AND ACCUMULATED DEPRECIATION
Beginning balance	$ 669,484	$ 591,136	$ 450,250
Purchase of real estate investments	48,305	82,111	143,141
Sale and disposal of real estate investment	(1,766)	(1,325)	(2,255)
Property held for sale	(3,234)	(2,058)
Provision for asset impairment	0	(412)	0
Construction in progress not yet placed in service	2,511
Reallocation to intangible assets		32
Ending balance	$ 715,300	$ 669,484	$ 591,136