PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Fair Value of Derivatives held by Pension Trusts (Details) - Pension - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Derivatives, Fair Value, Net	$ 378	$ 454
Equity and fixed income index derivatives, net
Defined Benefit Plan Disclosure [Line Items]
Derivatives, Fair Value, Net	10	3
Foreign currency derivatives, net
Defined Benefit Plan Disclosure [Line Items]
Derivatives, Fair Value, Net	(5)	(37)
Total return swaps, net
Defined Benefit Plan Disclosure [Line Items]
Derivatives, Fair Value, Net	$ 373	$ 488