EMPLOYEE BENEFITS (Narrative) (Details)		12 Months Ended
	Jan. 01, 2017 USD ($)	Dec. 31, 2020 USD ($) program investment_manager	Dec. 31, 2019 USD ($)	Jan. 01, 2019	Dec. 31, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of programs offered under health and dental benefit plan | program		2
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Eligibility, minimum required service period		1 year
Eligibility, minimum age		21 years
Estimated employer contribution in next fiscal year		$ 10,000,000
Retirement plan, employee deductible	$ 500
Percentage of retirement plan owed by employees 65 or older	50.00%
Percentage of retirement plan owed by employees less 65	100.00%
Percentage of retirement plan				100.00%
Benefit obligation		$ 271,744,000	$ 252,374,000		$ 202,156,000
Number of external investment managers | investment_manager		6
Post-retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation		$ 31,666,000	$ 31,001,000		$ 30,973,000