EMPLOYEE BENEFITS (Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits
Net periodic benefit cost
Service cost	$ 6,490	$ 6,675	$ 5,210
Interest cost	6,654	5,999	5,874
Expected return on plan assets	(7,952)	(7,800)	(6,956)
Amortization of net loss	3,968	4,546	2,174
Net periodic benefit cost	9,160	9,420	6,302
Post-retirement Benefits
Net periodic benefit cost
Service cost	3,728	5,220	3,696
Interest cost	3,015	2,856	2,342
Expected return on plan assets	0	0	0
Amortization of net loss	1,518	2,920	898
Net periodic benefit cost	$ 8,261	$ 10,996	$ 6,936