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 investments, at cost:
Balance, beginning of year	$ 1,323,384	$ 1,158,808	$ 1,053,678
Acquisitions	454,445	167,812	151,897
Improvements	20,768	16,784	21,296
Assets held for sale		(8,007)	(27,324)
Dispositions	(8,007)	(20,020)	(68,063)
Balance-Real Estate	1,790,590	1,315,377	1,131,484
Assets held for sale		8,007	27,324
Balance, end of year	1,790,590	1,323,384	1,158,808
Accumulated depreciation:
Balance, beginning of year	180,756	152,587	125,741
Depreciation	41,763	33,563	29,729
Assets held for sale		(167)	(4,354)
Dispositions	(267)	(5,394)	(2,883)
Balance- Accumulated Depreciation	222,252	180,589	148,233
Assets held for sale		167	4,354
Balance, end of year	$ 222,252	$ 180,756	$ 152,587