Segment Information (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Reconciliation of consolidated net operating income
Consolidated net operating income	$ 84,272	$ 84,842	$ 168,882	$ 167,120
Less:
Interest expense	(32,981)	(34,738)	(67,125)	(67,131)
Deferred financing costs	(1,261)	(1,070)	(2,572)	(1,998)
Depreciation and amortization	(49,331)	(55,710)	(98,880)	(105,214)
Administrative expenses	(6,079)	(5,890)	(12,129)	(12,134)
Plus:
Interest income	1,841	421	2,324	862
Interest expense — financing obligation	(196)	0	(378)	0
Equity in income of real estate ventures	838	1,088	882	2,321
Net gain on sales of interests in real estate ventures	0	0	0	2,791
Gain (loss) on early extinguishment of debt	(1,250)	(756)	(1,498)	(756)
Income (loss) from continuing operations	(4,147)	(11,813)	(10,494)	(14,139)
Income from discontinued operations	10,949	5,579	26,632	7,415
Net income (loss)	$ 6,802	$ (6,234)	$ 16,138	$ (6,724)