PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Basis of Fair Value Measurements of Pension Plan Assets) (Details) - Defined Benefit Pension Plans [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 21,208	$ 23,401	$ 18,774
Defined Benefit Plan, Fair Value of Plan Assets Subtotal	21,295	23,510
Defined Benefit Plan, Fair Value of Plan Assets, Reconciling Items, Pension Trust Receivables	38	27
Defined Benefit Plan, Fair Value of Plan Assets, Reconciling Items, Pension Trust Payables	(125)	(136)
Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets Subtotal	8,224	9,187
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets Subtotal	8,809	9,745
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,262	4,578	3,880
Defined Benefit Plan, Fair Value of Plan Assets Subtotal	4,262	4,578
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	879	772
Defined Benefit Plan, Fair Value of Plan Assets, Increase (Decrease) for Assets Transferred Into (Out of) Level 2	(794)
Cash and Cash Equivalents [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	867	671
Cash and Cash Equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12	101
Cash and Cash Equivalents [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,933	9,306
Defined Benefit Plan, Fair Value of Plan Assets, Increase (Decrease) for Assets Transferred Into (Out of) Level 2	(1,646)
Equity Securities [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,772	7,949
Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,128	1,317
Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33	40	28
US Treasury and Government [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,970	4,596
US Treasury and Government [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	136	158
US Treasury and Government [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,834	4,437
US Treasury and Government [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1
Corporate Bonds - Investment Grade [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,187	3,300
Corporate Bonds - Investment Grade [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	306	351
Corporate Bonds - Investment Grade [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,866	2,935
Corporate Bonds - Investment Grade [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15	14
Other Asset-backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	97	101
Other Asset-backed Securities [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Asset-backed Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	95	100
Other Asset-backed Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	1
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,254	7,997
Defined Benefit Plan, Fair Value of Plan Assets, Increase (Decrease) for Assets Transferred Into (Out of) Level 2	(442)
Fixed Income Securities [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	442	509
Fixed Income Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,795	7,472
Fixed Income Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17	16	17
Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,878	5,160
Defined Benefit Plan, Fair Value of Plan Assets, Increase (Decrease) for Assets Transferred Into (Out of) Level 2	(92)
Alternative Investments [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	113	21
Alternative Investments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	648	619
Alternative Investments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,117	4,520	3,797
Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,670	1,593
Hedge Funds [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	92	0
Hedge Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	631	663
Hedge Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	947	930
Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,128	1,390
Private Equity Funds [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Private Equity Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Private Equity Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,128	1,390
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,087	2,221
Real Estate [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21	21
Real Estate [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24	0
Real Estate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,042	2,200
Derivative Financial Instruments, Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	367	261
Derivative Financial Instruments, Assets [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	2
Derivative Financial Instruments, Assets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	365	259
Derivative Financial Instruments, Assets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Derivative Financial Instruments, Liabilities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(374)	(305)
Derivative Financial Instruments, Liabilities [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(2)	(2)
Derivative Financial Instruments, Liabilities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(372)	(303)
Derivative Financial Instruments, Liabilities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	351	275
Defined Benefit Plan, Fair Value of Plan Assets, Increase (Decrease) for Assets Transferred Into (Out of) Level 2	(30)
Other Investments [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	30	37
Other Investments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	226	236
Other Investments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	95	2	$ 38
UNITED STATES | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,645	3,755
UNITED STATES | Equity Securities [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,208	3,416
UNITED STATES | Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	436	339
UNITED STATES | Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0
Non-US [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,288	5,551
Non-US [Member] | Equity Securities [Member] | Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,564	4,533
Non-US [Member] | Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	692	978
Non-US [Member] | Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 32	$ 40