Schedule III - Real Estate and Accumulated Depreciation (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
ASSET BASIS
Balance at beginning of period	$ 1,683,803	$ 1,527,569	$ 1,349,088
Additions to land, buildings and improvements	290,486	273,902	263,182
Disposition of land, buildings and improvements	(125,039)	(116,553)	(75,454)
Impairment loss	(577)	(1,115)	(9,247)
Balance at end of period	1,848,673	1,683,803	1,527,569
ACCUMULATED DEPRECIATION
Balance at beginning of period	212,207	179,455	173,149
Depreciation	72,063	63,675	63,669
Depreciation on assets sold or disposed	(42,510)	(30,923)	(57,363)
Balance at end of period	241,760	$ 212,207	$ 179,455
Aggregate cost of land, buildings, furniture and equipment for federal income tax purposes	$ 1,384,100
Buildings and improvements | Minimum
ACCUMULATED DEPRECIATION
Useful lives	6 years
Buildings and improvements | Maximum
ACCUMULATED DEPRECIATION
Useful lives	40 years
Furniture, fixtures and equipment | Minimum
ACCUMULATED DEPRECIATION
Useful lives	2 years
Furniture, fixtures and equipment | Maximum
ACCUMULATED DEPRECIATION
Useful lives	15 years