NET INCOME PER COMMON SHARE (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
NET INCOME PER COMMON SHARE
Anti-dilutive share options excluded from computation of earnings per share	24,950	32,612
Computation of net income per common share
Net income attributable to common stockholders	$ 31,425	$ 20,214
Add: Income allocated to noncontrolling interest - Preferred Operating Partnership and Operating Partnership	2,494	2,300
Subtract: Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership	(1,438)	(1,438)
Net income for diluted computations	$ 32,481	$ 21,076
Weighted average common shares outstanding:
Average number of common shares outstanding - basic	110,809,924	94,888,078
Operating Partnership units (in shares)	2,755,650	3,064,128
Preferred Operating Partnership units (in shares)	989,980	989,980
Shares related to Exchangeable senior notes and dilutive and cancelled stock options	411,533	985,166
Average number of common shares outstanding - diluted	114,967,087	99,927,352
Net income per common share
Basic (in dollars per share)	$ 0.28	$ 0.21
Diluted (in dollars per share)	$ 0.28	$ 0.21