Condensed Consolidated Statement of Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Series A Preferred Operating Partnership	Operating Partnership	Other	Par Value	Paid-in Capital	Accumulated Other Comprehensive Income (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	5,876				4	5,872
Issuance of common stock upon the exercise of options (in shares)					387,393
Restricted stock grants issued	1				1
Restricted stock grants issued (in shares)					132,802
Restricted stock grants cancelled (in shares)					(21,356)
Compensation expense related to stock-based awards	3,654					3,654
Purchase of additional equity interests in existing consolidated joint ventures	(1,150)			(635)		(515)
Issuance of exchangeable senior notes - equity component	14,496					14,496
Issuance of Operating Partnership units in conjuction with portfolio acquisition	68,471		68,471
Redemption of Operating Partnership units for cash	(41)		(41)
Net income	103,049	5,160	2,715	38				95,136
Other comprehensive income	17,989	153	417				17,419
Tax effect from vesting of restricted stock grants and stock option exercises	3,147					3,147
Distributions to Operating Partnership units held by noncontrolling interests	(8,901)	(5,351)	(3,550)
Distributions to other noncontrolling interests	(43)			(43)
Dividends paid on common stock at $1.05 per share	(116,712)							(116,712)
Balances at Sep. 30, 2013	$ 1,635,167	$ 29,880	$ 90,504	$ 474	$ 1,112	$ 1,766,691	$ 3,146	$ (256,640)
Balances (in shares) at Sep. 30, 2013	111,236,044				111,236,044