Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Allowance for doubtful accounts receivable	$ (3,442)	$ (4,819)
Series D preferred units, par value	$ 50,000,000	$ 50,000,000
Series D preferred units outstanding	500,000	500,000
Preferred units of Series 3-5, units outstanding	11,000,000	11,000,000
Preferred stock, liquidation preferences per share	$ 275,000,000	$ 275,000,000
General partner units, outstanding		81,886,872
Limited partner units, outstanding	177,164	177,164
Parent Company [Member]
Allowance for doubtful accounts receivable	3,442	4,819
Straight-line rent receivable allowance	2,075	1,396
Deferred costs accumulated amortization	71,265	69,158
Accumulated amortization of acquired lease intangible assets	15,588	13,996
Accumulated accretion of acquired lease intangible liabilities	4,750	11,010
Preferred stock, par value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred units of Series 3-5, units issued	11,000,000	11,000,000
Preferred units of Series 3-5, units outstanding	11,000,000	11,000,000
Preferred stock, liquidation preferences per share	$ 25	$ 25
Common stock, par value per share	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	89,921,858	81,886,872
Preferred units, aggregate redemption value	50	50
Exchangeable operating partnership units aggregate redemption value	6,665	7,483
Treasury stock, shares held at cost	338,714	347,482
Partnership Interest [Member]
Allowance for doubtful accounts receivable	3,862	4,819
Straight-line rent receivable allowance	2,087	1,396
Deferred costs accumulated amortization	68,656	69,158
Accumulated amortization of acquired lease intangible assets	14,562	13,996
Accumulated accretion of acquired lease intangible liabilities	$ 4,399	$ 11,010
Series D preferred units, par value	$ 100	$ 100
Series D units issued	500,000	500,000
Series D preferred units outstanding	500,000	500,000
Preferred units of general partner par value per unit	$ 0.01	$ 0.01
Preferred units of Series 3-5, units issued	11,000,000	11,000,000
Preferred units of Series 3-5, units outstanding	11,000,000	11,000,000
Preferred stock, liquidation preferences per share	$ 25	$ 25
General partner units, outstanding	89,913,234	81,886,872
Limited partner units, outstanding	177,164	177,164