NET INCOME PER COMMON SHARE (Details 2) (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
NET INCOME PER COMMON SHARE
Anti-dilutive share options excluded from computation of earnings per share (in shares)	122,321	1,902,695	99,482	2,387,550
Computation of net income per common share
Net income attributable to common stockholders	$ 10,609	$ 6,180	$ 18,910	$ 9,748
Add: Income allocated to noncontrolling interest - Preferred Operating Partnership and Operating Partnership	1,910	1,762	3,754	3,390
Subtract: Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership	(1,437)	(1,437)	(2,875)	(2,875)
Net income for diluted computations	$ 11,082	$ 6,505	$ 19,789	$ 10,263
Weighted average common shares outstanding:
Average number of common shares outstanding - basic (in shares)	91,439,042	87,367,967	89,733,518	87,122,064
Operating Partnership units (in shares)	3,049,935	3,627,368	3,049,935	3,627,368
Preferred Operating Partnership units (in shares)	989,980	989,980	989,980	989,980
Dilutive and cancelled stock options (in shares)	531,891	319,516	562,708	286,738
Average number of common shares outstanding - diluted (in shares)	96,010,848	92,304,831	94,336,141	92,026,150
Net income per common share
Basic (in dollars per share)	$ 0.12	$ 0.07	$ 0.21	$ 0.11
Diluted (in dollars per share)	$ 0.12	$ 0.07	$ 0.21	$ 0.11