EQUITY - Changes in common stock (Details) - shares	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Changes in Common Stock [Roll Forward]
Beginning common shares outstanding	86,793,521	86,149,720
Common Unit redemptions	53,636	114,947
Common stock issued for director fees	4,073	3,055
Forfeitures	(406)	(46,030)
Other	(61,622)	(36,385)
Ending common shares outstanding	87,267,662	86,536,592
Directors
Changes in Common Stock [Roll Forward]
Grants under the Equity Plan and to directors	32,180	30,440
Equity Plan
Changes in Common Stock [Roll Forward]
Grants under the Equity Plan and to directors	446,280	320,845