PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Net Pension Plan Assets, by Fair Value Hiearchy (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 4,920	$ 5,502
Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	330	557	$ 455
Hedge funds and related investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	10	4
Private equity and related investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	65	102	75
Accrued liabilities, net | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(17)	(16)
Pension
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,930	5,514	$ 5,351
U.S. | Fixed Income Investments, Government [Member] | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	426
U.S. | Fixed Income Investments, Government [Member] | Fair Value, Inputs, Level 1 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
U.S. | Fixed Income Investments, Government [Member] | Fair Value, Inputs, Level 2 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	426
U.S. | Fixed Income Investments, Government [Member] | Fair Value, Inputs, Level 3 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
U.S. | Cash and short-term investments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	287	582
U.S. | Cash and short-term investments | Fair Value, Inputs, Level 1 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	275	580
U.S. | Cash and short-term investments | Fair Value, Inputs, Level 2 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12	2
U.S. | Cash and short-term investments | Fair Value, Inputs, Level 3 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Common and preferred stock | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1
U.S. | Common and preferred stock | Fair Value, Inputs, Level 1 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1
U.S. | Common and preferred stock | Fair Value, Inputs, Level 2 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Common and preferred stock | Fair Value, Inputs, Level 3 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Fixed Income Investments [Member] | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,054
U.S. | Fixed Income Investments [Member] | Fair Value, Inputs, Level 1 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
U.S. | Fixed Income Investments [Member] | Fair Value, Inputs, Level 2 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,054
U.S. | Fixed Income Investments [Member] | Fair Value, Inputs, Level 3 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
U.S. | Hedge funds and related investments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,814	3,237
U.S. | Hedge funds and related investments | Fair Value, Inputs, Level 1 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	59
U.S. | Hedge funds and related investments | Fair Value, Inputs, Level 2 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Hedge funds and related investments | Fair Value, Inputs, Level 3 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	10
U.S. | Private equity and related investments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,079	1,222
U.S. | Private equity and related investments | Fair Value, Inputs, Level 1 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Private equity and related investments | Fair Value, Inputs, Level 2 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Private equity and related investments | Fair Value, Inputs, Level 3 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	65	102
U.S. | Derivative financial instruments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	277	476
U.S. | Derivative financial instruments | Fair Value, Inputs, Level 1 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Derivative financial instruments | Fair Value, Inputs, Level 2 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15	31
U.S. | Derivative financial instruments | Fair Value, Inputs, Level 3 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	262	445
U.S. | Investments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,937	5,518
U.S. | Investments | Fair Value, Inputs, Level 1 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	275	640
U.S. | Investments | Fair Value, Inputs, Level 2 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,507	33
U.S. | Investments | Fair Value, Inputs, Level 3 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	330	557
U.S. | Fixed Income Investments, Government [Member] | Hedge funds and related investments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
U.S. | Net asset value [Member] | Cash and short-term investments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Net asset value [Member] | Common and preferred stock | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Net asset value [Member] | Hedge funds and related investments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,811	3,168
U.S. | Net asset value [Member] | Private equity and related investments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,014	1,120
U.S. | Net asset value [Member] | Derivative financial instruments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Net asset value [Member] | Investments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,825	4,288
U.S. | Fixed Income Investments [Member] | Hedge funds and related investments | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Canada | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	12
Canada | Fair Value, Inputs, Level 1 | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	12
Canada | Fair Value, Inputs, Level 2 | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Canada | Fair Value, Inputs, Level 3 | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Canada | Cash and short-term investments | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	6
Canada | Cash and short-term investments | Fair Value, Inputs, Level 1 | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	6
Canada | Cash and short-term investments | Fair Value, Inputs, Level 2 | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Canada | Cash and short-term investments | Fair Value, Inputs, Level 3 | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Canada | Common and preferred stock | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	6
Canada | Common and preferred stock | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Canada | Common and preferred stock | Fair Value, Inputs, Level 1 | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	6
Canada | Common and preferred stock | Fair Value, Inputs, Level 1 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Canada | Common and preferred stock | Fair Value, Inputs, Level 2 | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Canada | Common and preferred stock | Fair Value, Inputs, Level 2 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Canada | Common and preferred stock | Fair Value, Inputs, Level 3 | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Canada | Common and preferred stock | Fair Value, Inputs, Level 3 | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Canada | Net asset value [Member] | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Canada | Net asset value [Member] | Cash and short-term investments | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Canada | Net asset value [Member] | Common and preferred stock | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	$ 0
Canada | Net asset value [Member] | Common and preferred stock | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0