PENSION AND OTHER POSTRETIREMENT BENEFITS - CONTRIBUTIONS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
Pension contribution	$ 15,000,000	$ 0	$ 12,700,000
Pension Benefits [Member]
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2016	11,409,000
2017	11,846,000
2018	12,376,000
2019	13,374,000
2020	13,954,000
2021- 2024	82,139,000
Pension contribution	15,000,000	0	12,700,000
Employer contributions	17,017,000	1,535,000
Other Postretirement Benefits [Member]
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2016	4,458,000
2017	4,427,000
2018	4,363,000
2019	4,406,000
2020	4,519,000
2021- 2024	21,933,000
Employer contributions	8,721,000	4,773,000
Expected contribution to plan	3,600,000
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
Employer contributions	2,000,000	$ 1,500,000	$ 1,300,000
Expected contribution to plan	$ 2,300,000