PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Net Pension Plan Assets, by Fair Value Hiearchy (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 455	$ 546	$ 495
Hedge funds and related investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	3	5
Private equity and related investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	75	52	65
Qualified and Registered Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,341	5,481
Qualified and Registered Pension Plans | Cash and short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	731	722
Qualified and Registered Pension Plans | Cash and short-term investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	715	676
Qualified and Registered Pension Plans | Cash and short-term investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16	46
Qualified and Registered Pension Plans | Cash and short-term investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Common and preferred stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	0
Qualified and Registered Pension Plans | Common and preferred stock | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	0
Qualified and Registered Pension Plans | Common and preferred stock | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Common and preferred stock | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Hedge funds and related investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	66	90
Qualified and Registered Pension Plans | Hedge funds and related investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	62	87
Qualified and Registered Pension Plans | Hedge funds and related investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Hedge funds and related investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	3
Qualified and Registered Pension Plans | Private equity and related investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	75	52
Qualified and Registered Pension Plans | Private equity and related investments | 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 investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Private equity and related investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	75	52
Qualified and Registered Pension Plans | Derivative financial instruments, assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	386	495
Qualified and Registered Pension Plans | Derivative financial instruments, assets | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Derivative financial instruments, assets | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	4
Qualified and Registered Pension Plans | Derivative financial instruments, assets | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	376	491
Qualified and Registered Pension Plans | Derivative financial instruments, liabilities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(8)	(41)
Qualified and Registered Pension Plans | Derivative financial instruments, liabilities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Qualified and Registered Pension Plans | Derivative financial instruments, liabilities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(8)	(41)
Qualified and Registered Pension Plans | Derivative financial instruments, liabilities | 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	5,352	5,486
Qualified and Registered Pension Plans | Investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	784	763
Qualified and Registered Pension Plans | Investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18	9
Qualified and Registered Pension Plans | Investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	455	546
Qualified and Registered Pension Plans | Accrued liabilities, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(11)	(5)
Non Registered Canadian Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	10
Non Registered Canadian Pension Plans | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	10
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 and short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	6
Non Registered Canadian Pension Plans | Cash and short-term investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	6
Non Registered Canadian Pension Plans | Cash and short-term investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Non Registered Canadian Pension Plans | Cash and short-term investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Non Registered Canadian Pension Plans | Common and preferred stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4
Non Registered Canadian Pension Plans | Common and preferred stock | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4
Non Registered Canadian Pension Plans | Common and preferred stock | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Non Registered Canadian Pension Plans | Common and preferred stock | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Non Registered Canadian Pension Plans | Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5
Non Registered Canadian Pension Plans | Investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5
Non Registered Canadian Pension Plans | Investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Non Registered Canadian Pension Plans | Investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Pension
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,351	5,491	$ 5,643
Net asset value [Member] | Qualified and Registered Pension Plans | Hedge funds and related investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,957	2,893
Net asset value [Member] | Qualified and Registered Pension Plans | Private equity and related investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1,138	$ 1,275