EARNINGS PER COMMON SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator for basic and diluted earnings per share:
Income from continuing operations attributable to common stockholders, including real estate dispositions	$ 109,391	$ 127,470	$ 366,060	$ 381,233
Discontinued operations	(259)	(9,174)	2,517	(36,164)
Net income attributable to common stockholders	$ 109,132	$ 118,296	$ 368,577	$ 345,069
Denominator:
Denominator for basic earnings per share - weighted average shares	294,030	292,818	293,965	292,308
Effect of dilutive securities:
Stock options (in shares)	492	483	468	578
Restricted stock awards (in shares)	47	75	51	114
OP units (in shares)	1,926	1,814	1,927	1,788
Denominator for diluted earnings per share - adjusted weighted average shares	296,495	295,190	296,411	294,788
Basic earnings per share:
Income from continuing operations attributable to common stockholders, including real estate dispositions	$ 0.37	$ 0.43	$ 1.24	$ 1.30
Discontinued operations (in dollars per share)	$ 0.00	$ (0.03)	$ 0.01	$ (0.12)
Net income attributable to common stockholders	$ 0.37	$ 0.40	$ 1.25	$ 1.18
Diluted earnings per share:
Income from continuing operations attributable to common stockholders, including real estate dispositions	$ 0.37	$ 0.43	$ 1.23	$ 1.29
Discontinued operations	$ 0.00	$ (0.03)	$ 0.01	$ (0.12)
Net income attributable to common stockholders	$ 0.37	$ 0.40	$ 1.24	$ 1.17