SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Real Estate Properties
Balance at the beginning of the period	$ 1,467,863	$ 1,288,453	$ 911,327
Additions	103,413	192,560	378,176
Disposals	(2,714)	(13,150)	(1,050)
Balance at the end of the period	1,568,562	1,467,863	1,288,453
Accumulated Depreciation
Balance at the beginning of the period	156,661	139,210	115,215
Additions	33,688	30,601	25,045
Disposals	(2,714)	(13,150)	(1,050)
Balance at the end of the period	$ 187,635	$ 156,661	$ 139,210