EQUITY - Changes in common stock (Details) - shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Changes in Common Stock [Roll Forward]
Beginning common shares outstanding	93,525,469	86,793,521
Common Unit redemptions	10,657	31,042
Common stock issued for director fees	1,259	2,062
Shares retained for employee tax withholding requirements	(42,355)	(53,059)
Ending common shares outstanding	93,811,172	87,219,846
Equity Plan
Changes in Common Stock [Roll Forward]
Grants under the Equity Plan	316,142	446,280