PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Assets Within Our Qualified and Registered Pension Plans (Details) - Qualified and Registered Pension Plans	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	100.00%	100.00%
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	13.10%	12.20%
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	62.70%	60.60%
Private equity and related funds
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	23.00%	25.30%
Real estate and related funds
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	1.20%	1.40%
Common and preferred stock and equity index instruments
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	0.10%	0.70%
Accrued liabilities
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	(0.10%)	(0.20%)