PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Nonunion) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) person	Mar. 31, 2016 USD ($)
Pension and other postretirement benefit plans
Pension settlement expense, pre-tax	$ 1,957	$ 900
Pension settlement expense, net of tax	$ 1,196	550
Nonunion Defined Benefit Pension Plan
Pension and other postretirement benefit plans
Number of plan participants for which vested pension benefits were settled | person	50
Pension settlement expense, pre-tax	$ 1,957	900
Pension settlement expense, net of tax	1,200	600
Premium paid to purchase nonparticipating annuity contract	7,600
Lump-sum distributions	$ 4,800	$ 4,500