PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Actual Returns on Assets Held by Our Pension Trusts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Actual return on plan assets	$ 368	$ 808	$ 490
Direct investments
Defined Benefit Plan Disclosure [Line Items]
Actual return on plan assets	258	568	324
Derivatives
Defined Benefit Plan Disclosure [Line Items]
Actual return on plan assets	$ 110	$ 240	$ 166