EMPLOYEE BENEFIT PLANS - Discount rate and assumptions (Details)	3 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Nonunion Defined Benefit Pension Plan
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	3.70%	3.80%			3.90%
Expected return on plan assets, net of estimated expenses (as a percent)	0.00%	0.00%			1.40%
Supplemental Benefit Plan
Weighted-average assumptions used to determine nonunion benefit obligations
Discount rate (as a percent)			1.80%	1.10%
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)			1.10%	2.40%	3.60%
Postretirement Health Benefit Plan
Weighted-average assumptions used to determine nonunion benefit obligations
Discount rate (as a percent)			2.70%	2.30%
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)			2.30%	3.10%	4.20%