PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Nonunion) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Mar. 31, 2018
Pension and other postretirement benefit plans
Pension settlement expense, pre-tax		$ 1,356	$ 654
Pension settlement expense, net of tax		1,007	486
Nonunion Defined Benefit Pension Plan
Pension and other postretirement benefit plans
Pension settlement expense, pre-tax		1,356	654
Pension settlement expense, net of tax		1,000	500
Lump-sum distributions		$ 14,900	$ 4,800
Expected return on plan assets (as a percent)		1.40%
Nonunion Defined Benefit Pension Plan | Forecast
Pension and other postretirement benefit plans
Pension settlement expense, pre-tax	$ 2,000
Pension settlement expense, after-tax	1,500
Employer contributions	$ 6,000
Expected return on plan assets (as a percent)	0.00%