PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Reconciliation of Pension Plan Assets (Details) (Fair Value, Inputs, Level 3, USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning	$ 4,935	$ 4,439
Net realized gains (losses)	322	235
Net change in unrealized appreciation (depreciation)	(58)	435
Purchases	723	960
Sales	(927)	(1,055)
Issuances	52
Settlements	(132)	(79)
Transfers, Out(1)	(75)
Fair value of plan assets, ending	4,840	4,935
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning	3,225	2,767
Net realized gains (losses)	186	164
Net change in unrealized appreciation (depreciation)	76	275
Purchases	541	743
Sales	(540)	(645)
Issuances	52
Settlements	(132)	(79)
Transfers, Out(1)	(75)
Fair value of plan assets, ending	3,333	3,225
Private equity and related funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning	1,606	1,577
Net realized gains (losses)	128	90
Net change in unrealized appreciation (depreciation)	(130)	138
Purchases	177	188
Sales	(359)	(387)
Issuances	0
Settlements	0	0
Transfers, Out(1)	0
Fair value of plan assets, ending	1,422	1,606
Real estate and related funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning	101	91
Net realized gains (losses)	8	(19)
Net change in unrealized appreciation (depreciation)	(4)	23
Purchases	5	29
Sales	(28)	(23)
Issuances	0
Settlements	0	0
Transfers, Out(1)	0
Fair value of plan assets, ending	82	101
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning	3	4
Net realized gains (losses)	0	0
Net change in unrealized appreciation (depreciation)	0	(1)
Purchases	0	0
Sales	0	0
Issuances	0
Settlements	0	0
Transfers, Out(1)	0
Fair value of plan assets, ending	$ 3	$ 3

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Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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