PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Pension Trusts' Net Investments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 4,935	$ 4,439	$ 4,159
Fixed income instruments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	4	4
Hedge funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,225	2,767	2,432
Private equity and related funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,606	1,577	1,627
Real estate and related funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	101	91	96
Qualified and Registered Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,600	5,008
Qualified and Registered Pension Plans | Fixed income instruments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	638	573
Qualified and Registered Pension Plans | Fixed income instruments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	567	476
Qualified and Registered Pension Plans | Fixed income instruments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	68	93
Qualified and Registered Pension Plans | Fixed income instruments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	4
Qualified and Registered Pension Plans | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,218	2,767
Qualified and Registered Pension Plans | Hedge funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Hedge funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(7)	0
Qualified and Registered Pension Plans | Hedge funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,225	2,767
Qualified and Registered Pension Plans | Private equity and related funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,604	1,575
Qualified and Registered Pension Plans | Private equity and related funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Private equity and related funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(2)	(2)
Qualified and Registered Pension Plans | Private equity and related funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,606	1,577
Qualified and Registered Pension Plans | Real estate and related funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	101	91
Qualified and Registered Pension Plans | Real estate and related funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Real estate and related funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Real estate and related funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	101	91
Qualified and Registered Pension Plans | Common and preferred stock and equity index instruments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52	21
Qualified and Registered Pension Plans | Common and preferred stock and equity index instruments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23	17
Qualified and Registered Pension Plans | Common and preferred stock and equity index instruments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29	4
Qualified and Registered Pension Plans | Common and preferred stock and equity index instruments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,613	5,027
Qualified and Registered Pension Plans | Investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	590	493
Qualified and Registered Pension Plans | Investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	88	95
Qualified and Registered Pension Plans | Investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,935	4,439
Qualified and Registered Pension Plans | Accrued liabilities, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(13)	(19)
Non Registered Canadian Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	14
Non Registered Canadian Pension Plans | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	14
Non Registered Canadian Pension Plans | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Non Registered Canadian Pension Plans | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Non Registered Canadian Pension Plans | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8	8
Non Registered Canadian Pension Plans | Cash | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8	8
Non Registered Canadian Pension Plans | Cash | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Non Registered Canadian Pension Plans | Cash | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Non Registered Canadian Pension Plans | Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	6
Non Registered Canadian Pension Plans | Investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	6
Non Registered Canadian Pension Plans | Investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Non Registered Canadian Pension Plans | Investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,614	5,022	4,714
Pension | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 4,900