Summary of Quarterly Results (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information [Line Items]
Real Estate Revenue, Net	$ 138,658,000	$ 143,354,000	$ 140,644,000	$ 139,554,000	$ 136,395,000	$ 134,238,000	$ 131,530,000	$ 133,516,000	$ 562,210,000	$ 535,679,000	$ 538,568,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	21,002,000	11,088,000	7,180,000	3,919,000	(26,698,000)	17,089,000	6,802,000	9,336,000	43,189,000	6,529,000	(4,715,000)
Net Income (Loss) Attributable to Parent	18,975,000	9,173,000	5,308,000	2,058,000	(30,832,000)	13,949,000	1,537,000	7,108,000	42,777,000	6,595,000	(4,499,000)
Earnings Per Share, Basic	$ 0.12	$ 0.06	$ 0.03	$ 0.01	$ (0.21)	$ 0.10	$ 0.01	$ 0.05	$ 0.23	$ (0.06)	$ (0.10)
Earnings Per Share, Diluted	$ 0.12	$ 0.06	$ 0.03	$ 0.01	$ (0.21)	$ 0.10	$ 0.01	$ 0.05	$ 0.23	$ (0.06)	$ (0.10)
Restatement Adjustment [Member]
Quarterly Financial Information [Line Items]
Out of period stock compensation expense adjustment					600,000
Overstatement (Understatement) of Expense due to Out of Period Adjustment					$ 600,000	$ (200,000)	$ (300,000)				$ (100,000)