Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Parent Company [Member]
Allowance for doubtful accounts receivable	$ 5,304	$ 5,295
Straight-line rent receivable allowance	1,421	1,365
Deferred costs accumulated amortization	78,852	76,823
Accumulated amortization of acquired lease intangible assets	47,470	45,639
Accumulated Accretion	$ 18,603	$ 17,555
Preferred stock, par value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred units of Series 6-7, units issued	13,000,000	13,000,000
Preferred units of Series 6-7, units outstanding	13,000,000	13,000,000
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	97,610,485	97,212,638
Exchangeable operating partnership units aggregate redemption value	$ 11,540	$ 10,502
Treasury stock, shares held at cost	382,969	417,862
Partnership Interest [Member]
Allowance for doubtful accounts receivable	$ 5,304	$ 5,295
Straight-line rent receivable allowance	1,421	1,365
Deferred costs accumulated amortization	78,852	76,823
Accumulated amortization of acquired lease intangible assets	47,470	45,639
Accumulated accretion of acquired lease intangible liabilities	$ 18,603	$ 17,555
Preferred units of general partner par value per unit	$ 0.01	$ 0.01
Preferred units of Series 6-7, units issued	13,000,000	13,000,000
Preferred units of Series 6-7, units outstanding	13,000,000	13,000,000
Preferred stock, liquidation preferences per share	$ 25	$ 25
General partner units, outstanding	97,610,485	97,212,638
Limited partner units, outstanding	154,170	154,170