Condensed Consolidated Statement of Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Preferred Operating Partnership	Operating Partnership	Other	Par Value	Paid-in Capital	Accumulated Other Comprehensive Deficit	Accumulated Deficit
Balances at Dec. 31, 2012	$ 1,545,331	$ 29,918	$ 22,492	$ 1,114	$ 1,107	$ 1,740,037	$ (14,273)	$ (235,064)
Balances (in shares) at Dec. 31, 2012	110,737,205				110,737,205
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon the exercise of options	1,635				1	1,634
Issuance of common stock upon the exercise of options (in shares)					124,371
Restricted stock grants issued	1				1
Restricted stock grants issued (in shares)					70,105
Restricted stock grants cancelled (in shares)					(6,685)
Compensation expense related to stock-based awards	1,023					1,023
Purchase of additional equity interest in existing consolidated joint venture	(200)			(75)		(125)
Redemption of Operating Partnership units for cash	(20)		(20)
Net income	33,931	1,717	777	12				31,425
Other comprehensive income	1,571	14	43				1,514
Distributions to Operating Partnership units held by noncontrolling interests	(2,374)	(1,685)	(689)
Distributions to other noncontrolling interests	(16)			(16)
Dividends paid on common stock at $0.25 per share	(27,730)							(27,730)
Balances at Mar. 31, 2013	$ 1,553,152	$ 29,964	$ 22,603	$ 1,035	$ 1,109	$ 1,742,569	$ (12,759)	$ (231,369)
Balances (in shares) at Mar. 31, 2013	110,924,996				110,924,996