EQUITY - Changes in common stock (Details) - shares	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Changes in Common Stock [Roll Forward]
Beginning common shares outstanding	93,525,469	86,793,521
Stock Offering	10,350,000	0
Common Unit redemptions	30,657	53,636
Common stock issued for director fees	2,454	4,073
Forfeitures	(1,237)	(406)
Shares retained for employee tax withholding requirements	(59,111)	(61,622)
Ending common shares outstanding	104,238,807	87,267,662
Directors
Changes in Common Stock [Roll Forward]
Grants under the equity compensation plans	23,896	32,180
Equity Plan
Changes in Common Stock [Roll Forward]
Grants under the equity compensation plans	366,679	446,280