EQUITY - Changes in common stock (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Changes in Common Stock [Roll Forward]
Beginning common shares outstanding	104,783,179	104,287,128
Grants under the Equity Plan	537,304	583,373
Common stock issued for director fees	0	1,147
Performance share and other forfeitures	(166,478)	0
Shares retained for employee tax withholding requirements	(73,892)	(187,850)
Ending common shares outstanding	105,080,113	104,683,798