EARNINGS PER COMMON SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator for basic and diluted earnings per share:
Income from continuing operations attributable to common stockholders, including real estate dispositions	$ 138,653	$ 133,139	$ 256,669	$ 253,763
Discontinued operations	(255)	(18,559)	2,776	(26,990)
Net income attributable to common stockholders	$ 138,398	$ 114,580	$ 259,445	$ 226,773
Denominator:
Denominator for basic earnings per share - weighted average shares	293,988	292,635	293,932	292,049
Effect of dilutive securities:
Stock options (in shares)	530	567	456	627
Restricted stock awards (in shares)	59	148	53	134
OP units (in shares)	1,927	1,773	1,928	1,774
Denominator for diluted earnings per share - adjusted weighted average shares	296,504	295,123	296,369	294,584
Basic earnings per share:
Income from continuing operations attributable to common stockholders, including real estate dispositions	$ 0.47	$ 0.45	$ 0.87	$ 0.87
Discontinued operations (in dollars per share)	$ 0.00	$ (0.06)	$ 0.01	$ (0.09)
Net income attributable to common stockholders	$ 0.47	$ 0.39	$ 0.88	$ 0.78
Diluted earnings per share:
Income from continuing operations attributable to common stockholders, including real estate dispositions	$ 0.47	$ 0.45	$ 0.87	$ 0.86
Discontinued operations	$ 0.00	$ (0.06)	$ 0.01	$ (0.09)
Net income attributable to common stockholders	$ 0.47	$ 0.39	$ 0.88	$ 0.77