RETIREMENT BENEFITS - Funded Status and Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
U.S. | Pension Plans
Change in projected benefit obligation
Projected benefit obligation at beginning of year		$ 14,000		$ 14,000
Projected benefit obligation at June 30, 2017—Significant Plans	$ 14,158			14,158
Change in plan assets
Plan assets at fair value at beginning of year		12,363		12,363
Plan assets at fair value at June 30, 2017—Significant Plans	12,708			12,708
Funded status of the Significant Plans	(1,450)			(1,450)
Net amount recognized
Benefit asset	0			0
Benefit liability	(1,450)			(1,450)
Net amount recognized on the balance sheet—Significant Plans	(1,450)			(1,450)
Amounts recognized in AOCI
Prior service benefit	0			0
Net actuarial gain (loss)	(6,821)			(6,821)
Net amount recognized in equity-pretax	(6,821)			(6,821)
Accumulated benefit obligation at June 30, 2017—Significant Plans	14,151			14,151
U.S. | Pension Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation
Projected benefit obligation at beginning of year		28		28
Change in plan assets
Plan assets at fair value at beginning of year		0		0
U.S. | Pension Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation
Projected benefit obligation at beginning of year	13,997	13,972		13,972
First quarter activity		25
Benefits earned during the period	0
Interest cost on benefit obligation	135
Actuarial gain (loss)	214
Benefits paid, net of participants’ contributions	(191)
Curtailment loss	3
Foreign exchange impact and other	0
Projected benefit obligation at June 30, 2017—Significant Plans		13,997
Change in plan assets
Plan assets at fair value at beginning of year	12,522	12,363		12,363
First quarter activity		159
Actual return on plan assets	364
Company contributions, net of reimbursements	13
Plan participants’ contributions	0
Benefits paid, net of government subsidy	(191)
Foreign exchange impact and other	0
Plan assets at fair value at June 30, 2017—Significant Plans		12,522
U.S. | Postretirement Benefit Plans
Change in projected benefit obligation
Projected benefit obligation at beginning of year		686		686
Projected benefit obligation at June 30, 2017—Significant Plans	742			742
Change in plan assets
Plan assets at fair value at beginning of year		129		129
Plan assets at fair value at June 30, 2017—Significant Plans	126			126
Funded status of the Significant Plans	(616)			(616)
Net amount recognized
Benefit asset	0			0
Benefit liability	(616)			(616)
Net amount recognized on the balance sheet—Significant Plans	(616)			(616)
Amounts recognized in AOCI
Prior service benefit	0			0
Net actuarial gain (loss)	39			39
Net amount recognized in equity-pretax	39			39
Accumulated benefit obligation at June 30, 2017—Significant Plans	742			742
U.S. | Postretirement Benefit Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation
Projected benefit obligation at beginning of year		0		0
Change in plan assets
Plan assets at fair value at beginning of year		0		0
U.S. | Postretirement Benefit Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation
Projected benefit obligation at beginning of year	679	686		686
First quarter activity		(7)
Benefits earned during the period	0
Interest cost on benefit obligation	7
Actuarial gain (loss)	71
Benefits paid, net of participants’ contributions	(15)
Curtailment loss	0
Foreign exchange impact and other	0
Projected benefit obligation at June 30, 2017—Significant Plans		679
Change in plan assets
Plan assets at fair value at beginning of year	129	129		129
First quarter activity		0
Actual return on plan assets	4
Company contributions, net of reimbursements	8
Plan participants’ contributions	0
Benefits paid, net of government subsidy	(15)
Foreign exchange impact and other	0
Plan assets at fair value at June 30, 2017—Significant Plans		129
Non-U.S. plans | Pension Plans
Change in projected benefit obligation
Projected benefit obligation at beginning of year		6,522		6,522
Projected benefit obligation at June 30, 2017—Significant Plans	5,549			5,549
Change in plan assets
Plan assets at fair value at beginning of year		6,149		6,149
Plan assets at fair value at June 30, 2017—Significant Plans	5,846			5,846
Funded status of the Significant Plans	297			297
Net amount recognized
Benefit asset	758			758
Benefit liability	(461)			(461)
Net amount recognized on the balance sheet—Significant Plans	297			297
Amounts recognized in AOCI
Prior service benefit	32			32
Net actuarial gain (loss)	(984)			(984)
Net amount recognized in equity-pretax	(952)			(952)
Accumulated benefit obligation at June 30, 2017—Significant Plans	5,280			5,280
Non-U.S. plans | Pension Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation
Projected benefit obligation at beginning of year		1,784		1,784
Change in plan assets
Plan assets at fair value at beginning of year		1,167		1,167
Non-U.S. plans | Pension Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation
Projected benefit obligation at beginning of year	5,540	4,738		4,738
First quarter activity		802
Benefits earned during the period	22
Interest cost on benefit obligation	62
Actuarial gain (loss)	(58)
Benefits paid, net of participants’ contributions	(79)
Curtailment loss	0
Foreign exchange impact and other	62
Projected benefit obligation at June 30, 2017—Significant Plans		5,540
Change in plan assets
Plan assets at fair value at beginning of year	5,885	4,982		4,982
First quarter activity		903
Actual return on plan assets	(45)
Company contributions, net of reimbursements	13
Plan participants’ contributions	1
Benefits paid, net of government subsidy	(80)
Foreign exchange impact and other	72
Plan assets at fair value at June 30, 2017—Significant Plans		5,885
Non-U.S. plans | Postretirement Benefit Plans
Change in projected benefit obligation
Projected benefit obligation at beginning of year		1,141		1,141
Projected benefit obligation at June 30, 2017—Significant Plans	1,044			1,044
Change in plan assets
Plan assets at fair value at beginning of year		1,015		1,015
Plan assets at fair value at June 30, 2017—Significant Plans	1,183			1,183
Funded status of the Significant Plans	139			139
Net amount recognized
Benefit asset	139			139
Benefit liability	0			0
Net amount recognized on the balance sheet—Significant Plans	139			139
Amounts recognized in AOCI
Prior service benefit	94			94
Net actuarial gain (loss)	(403)			(403)
Net amount recognized in equity-pretax	(309)			(309)
Accumulated benefit obligation at June 30, 2017—Significant Plans	1,044			1,044
Non-U.S. plans | Postretirement Benefit Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation
Projected benefit obligation at beginning of year		303		303
Change in plan assets
Plan assets at fair value at beginning of year		11		11
Non-U.S. plans | Postretirement Benefit Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation
Projected benefit obligation at beginning of year	972	838		838
First quarter activity		134
Benefits earned during the period	2
Interest cost on benefit obligation	22
Actuarial gain (loss)	22
Benefits paid, net of participants’ contributions	(14)
Curtailment loss	0
Foreign exchange impact and other	40
Projected benefit obligation at June 30, 2017—Significant Plans		972
Change in plan assets
Plan assets at fair value at beginning of year	1,128	1,004		1,004
First quarter activity		124
Actual return on plan assets	23
Company contributions, net of reimbursements	0
Plan participants’ contributions	0
Benefits paid, net of government subsidy	(14)
Foreign exchange impact and other	46
Plan assets at fair value at June 30, 2017—Significant Plans		$ 1,128
Qualified plans | U.S. | Pension Plans
Change in projected benefit obligation
Benefits earned during the period	0		$ 0	1	$ 1
Interest cost on benefit obligation	128		132	260	273
Change in plan assets
Funded status of the Significant Plans	(720)			(720)
Qualified plans | U.S. | Postretirement Benefit Plans
Change in projected benefit obligation
Benefits earned during the period	0		0	0	0
Interest cost on benefit obligation	8		5	14	13
Change in plan assets
Funded status of the Significant Plans	(616)			(616)
Qualified plans | Non-U.S. plans | Pension Plans
Change in projected benefit obligation
Benefits earned during the period	38		39	74	77
Interest cost on benefit obligation	74		73	145	146
Change in plan assets
Funded status of the Significant Plans	297			297
Qualified plans | Non-U.S. plans | Postretirement Benefit Plans
Change in projected benefit obligation
Benefits earned during the period	2		3	4	6
Interest cost on benefit obligation	25		$ 24	49	$ 48
Change in plan assets
Funded status of the Significant Plans	139			139
Nonqualified plans | U.S. | Pension Plans
Change in plan assets
Funded status of the Significant Plans	(730)			(730)
Nonqualified plans | U.S. | Postretirement Benefit Plans
Change in plan assets
Funded status of the Significant Plans	0			0
Nonqualified plans | Non-U.S. plans | Pension Plans
Change in plan assets
Funded status of the Significant Plans	0			0
Nonqualified plans | Non-U.S. plans | Postretirement Benefit Plans
Change in plan assets
Funded status of the Significant Plans	$ 0			$ 0