ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss recognized during settlement		$ 0
Net current-period other comprehensive income (loss) before income tax	$ (4,100)
Tax (benefit) expense	(6,500)	(5,700)
Net of tax	200
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Prior service credits	(200)	(200)
Actuarial losses	100	400
Loss recognized during settlement	200
Net current-period other comprehensive income (loss) before income tax	100	200
Tax (benefit) expense	0	0
Net of tax	$ 100	$ 200