BENEFIT PLANS (Employer Contributions for Plan) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 4,871	$ 5,280	$ 5,915
2018 (estimated)	5,624
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	20,023	9,576	$ 14,047
Employer contributions	51,234	$ 48,302
2018 (estimated)	$ 109,477