EQUITY - Changes in common stock (Details) - shares	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Changes in Common Stock [Roll Forward]
Beginning common shares outstanding	86,793,521	86,149,720
Common Unit redemptions	61,056	172,429
Common stock issued for director fees	5,851	4,716
Forfeitures	(406)	(46,030)
Shares retained for employee tax withholding requirements	(61,622)	(36,385)
Ending common shares outstanding	87,314,950	86,595,735
Directors
Changes in Common Stock [Roll Forward]
Grants under the Equity Plan	32,180	30,440
Equity Plan
Changes in Common Stock [Roll Forward]
Grants under the Equity Plan	446,686	320,845
Exercise of stock options	37,684	0