PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Nonunion) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Dec. 31, 2019	Jun. 30, 2019	Jun. 30, 2018
Pension and other postretirement benefit plans
Pension settlement expense						$ 1,634	$ 1,085
Pension settlement expense, net of tax		$ 206		$ 320		1,213	806
Nonunion Defined Benefit Pension Plan
Pension and other postretirement benefit plans
Pension settlement expense		278		431		1,634	1,085
Pension settlement expense, net of tax		200		300		1,200	800
Lump-sum distributions		$ 3,000		$ 3,700		$ 17,900	$ 8,500
Expected return on plan assets (as a percent)		0.00%	1.40%
Nonunion Defined Benefit Pension Plan | Forecast
Pension and other postretirement benefit plans
Pension settlement expense					$ 2,000
Pension settlement expense, net of tax					1,500
Employer contributions					$ 7,000
Expected return on plan assets (as a percent)	0.00%