Summary of Quarterly Results (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Financial Information [Line Items]
Real Estate Revenue, Net	$ 142,463,000	$ 140,383,000	$ 137,576,000	$ 139,411,000	$ 141,486,000	$ 139,401,000	$ 139,249,000	$ 141,617,000	$ 559,833,000	$ 561,753,000	$ 540,432,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(26,698,000)	17,089,000	6,802,000	9,336,000	(4,602,000)	6,611,000	(6,234,000)	(490,000)	6,529,000	(4,715,000)	(17,606,000)
Net Income (Loss) Attributable to Parent	(30,832,000)	13,949,000	1,537,000	7,108,000	(6,359,000)	4,130,000	(8,188,000)	(2,579,000)	6,595,000	(4,499,000)	(17,074,000)
Earnings Per Share, Basic	$ (0.21)	$ 0.10	$ 0.01	$ 0.05	$ (0.05)	$ 0.03	$ (0.06)	$ (0.02)	$ (0.06)	$ (0.10)	$ (0.19)
Earnings Per Share, Diluted	$ (0.21)	$ 0.10	$ 0.01	$ 0.05	$ (0.05)	$ 0.03	$ (0.06)	$ (0.02)	$ (0.06)	$ (0.10)	$ (0.19)
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)