NET INCOME PER COMMON SHARE (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net income per common share
Anti-dilutive share options excluded from computation of earnings per share	51,036	15,223	43,273	54,959
Computation of net income per common share
Net income attributable to common stockholders	$ 29,245	$ 38,606	$ 95,136	$ 81,233
Add: Income allocated to noncontrolling interest - Preferred Operating Partnership and Operating Partnership	3,092	2,938	8,210	7,563
Subtract: Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership	(1,438)	(1,438)	(4,313)	(4,313)
Net income for diluted computations	$ 30,899	$ 40,106	$ 99,033	$ 84,483
Weighted average common shares outstanding:
Average number of common shares outstanding - basic	111,231,452	104,252,227	111,060,997	100,429,840
Operating Partnership units (in shares)	4,346,618	3,060,467	4,346,618	3,060,467
Shares related to dilutive and cancelled stock options (in shares)	302,734	452,642	351,684	500,889
Average number of common shares outstanding - diluted	117,604,515	108,755,316	117,483,010	104,981,176
Net income per common share
Basic (in dollars per share)	$ 0.26	$ 0.37	$ 0.86	$ 0.81
Diluted (in dollars per share)	$ 0.26	$ 0.37	$ 0.84	$ 0.80
Series B Preferred Operating Partnership
Weighted average common shares outstanding:
Preferred Operating Partnership units (in shares)	733,731		733,731
Series A Preferred Operating Partnership
Weighted average common shares outstanding:
Preferred Operating Partnership units (in shares)	989,980	989,980	989,980	989,980