Schedule III - Real Estate and Accumulated Depreciation (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
ASSET BASIS
Balance at the beginning of the period	$ 901,207,000	$ 645,339,000	$ 570,807,000
Additions to land, buildings and improvements	531,207,000	294,310,000	79,901,000
Disposition of land, buildings and improvements	(74,282,000)	(35,477,000)	(5,369,000)
Impairment loss	(9,044,000)	(2,965,000)
Balance at the end of the period	1,349,088,000	901,207,000	645,339,000
ACCUMULATED DEPRECIATION
Balance at the beginning of the period	146,207,000	126,168,000	104,797,000
Depreciation	50,445,000	31,732,000	26,740,000
Depreciation on assets sold or disposed	(23,503,000)	(11,693,000)	(5,369,000)
Balance at the end of the period	173,149,000	146,207,000	126,168,000
Real estate and accumulated depreciation
Aggregate cost of land, buildings, furniture and equipment for federal income tax purposes	$ 1,317,000,000
Buildings and improvements | Minimum
Real estate and accumulated depreciation
Useful lives	25 years
Buildings and improvements | Maximum
Real estate and accumulated depreciation
Useful lives	40 years
Furniture and equipment | Minimum
Real estate and accumulated depreciation
Useful lives	2 years
Furniture and equipment | Maximum
Real estate and accumulated depreciation
Useful lives	15 years