Consolidated Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues:
Property rental	$ 268,725	$ 232,447	$ 238,256
Management and franchise fees	29,924	23,122	20,961
Tenant reinsurance	31,181	25,928	20,929
Total revenues	329,830	281,497	280,146
Expenses:
Property operations	95,481	86,165	88,935
Tenant reinsurance	6,143	6,505	5,461
Unrecovered development and acquisition costs	2,896	1,235	19,011
Loss on sublease		2,000
Severance costs	2,137		2,225
General and administrative	49,683	44,428	40,224
Depreciation and amortization	58,014	50,349	52,403
Total expenses	214,354	190,682	208,259
Income from operations	115,476	90,815	71,887
Interest expense	(67,301)	(64,116)	(67,579)
Non-cash interest expense related to amortization of discount on exchangeable senior notes	(1,761)	(1,664)	(2,239)
Interest income	1,027	898	1,582
Interest income on note receivable from Preferred Operating Partnership unit holder	4,850	4,850	4,850
Gain on repurchase of exchangeable senior notes			27,928
Income before equity in earnings of real estate ventures and income tax expense	52,291	30,783	36,429
Equity in earnings of real estate ventures	7,287	6,753	6,964
Income tax expense	(1,155)	(4,162)	(4,300)
Net income	58,423	33,374	39,093
Net income allocated to Preferred Operating Partnership noncontrolling interests	(6,289)	(6,048)	(6,186)
Net income allocated to Operating Partnership and other noncontrolling interests	(1,685)	(995)	(930)
Net income attributable to common stockholders	$ 50,449	$ 26,331	$ 31,977
Net income per common share
Basic (in dollars per share)	$ 0.55	$ 0.30	$ 0.37
Diluted (in dollars per share)	$ 0.54	$ 0.30	$ 0.37
Weighted average number of shares
Basic (in shares)	92,097,008	87,324,104	86,343,029
Diluted (in shares)	96,683,508	92,050,453	91,082,834
Cash dividends paid per common share (in dollars per share)	$ 0.56	$ 0.40	$ 0.38