RETIREMENT BENEFITS - Funded Status and Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
U.S. Pension Plans
Change in projected benefit obligation
Projected benefit obligation at beginning of year	$ 14,000
Projected benefit obligation at period end—Significant Plans	13,997
Change in plan assets
Plan assets at fair value at beginning of year	12,363
Plan assets at fair value at period end—Significant Plans	12,522
Funded status of the Significant Plans	(1,475)
Net amount recognized
Benefit asset	0
Benefit liability	(1,475)
Net amount recognized on the balance sheet—Significant Plans	(1,475)
Amounts recognized in AOCI
Prior service benefit	0
Net actuarial gain (loss)	(6,795)
Net amount recognized in equity-pretax	(6,795)
Accumulated benefit obligation at period end—Significant Plans	13,991
U.S. Pension Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation
Projected benefit obligation at beginning of year	28
Change in plan assets
Plan assets at fair value at beginning of year	0
U.S. Pension Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation
Projected benefit obligation at beginning of year	13,972
Benefits earned during the period	1
Interest cost on benefit obligation	139
Plan amendments	0
Actuarial loss	72
Benefits paid, net of participants’ contributions	(187)
Foreign exchange impact and other	0
Change in plan assets
Plan assets at fair value at beginning of year	12,363
Actual return on plan assets	333
Company contributions, net of reimbursements	13
Plan participants’ contributions	0
Benefits paid, net of government subsidy	(187)
Foreign exchange impact and other	0
U.S. Qualified Pension Plan
Change in projected benefit obligation
Benefits earned during the period	1	$ 1
Interest cost on benefit obligation	132	141
Change in plan assets
Funded status of the Significant Plans	(778)
U.S. Nonqualified Pension Plan
Change in plan assets
Funded status of the Significant Plans	(697)
Non-U.S. Pension Plans
Change in projected benefit obligation
Projected benefit obligation at beginning of year	6,522
Projected benefit obligation at period end—Significant Plans	5,540
Change in plan assets
Plan assets at fair value at beginning of year	6,149
Plan assets at fair value at period end—Significant Plans	5,885
Funded status of the Significant Plans	345
Net amount recognized
Benefit asset	801
Benefit liability	(456)
Net amount recognized on the balance sheet—Significant Plans	345
Amounts recognized in AOCI
Prior service benefit	32
Net actuarial gain (loss)	(921)
Net amount recognized in equity-pretax	(889)
Accumulated benefit obligation at period end—Significant Plans	5,272
Non-U.S. Pension Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation
Projected benefit obligation at beginning of year	1,784
Change in plan assets
Plan assets at fair value at beginning of year	1,167
Non-U.S. Pension Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation
Projected benefit obligation at beginning of year	4,738
Benefits earned during the period	21
Interest cost on benefit obligation	60
Plan amendments	5
Actuarial loss	134
Benefits paid, net of participants’ contributions	(75)
Foreign exchange impact and other	657
Change in plan assets
Plan assets at fair value at beginning of year	4,982
Actual return on plan assets	179
Company contributions, net of reimbursements	13
Plan participants’ contributions	1
Benefits paid, net of government subsidy	(76)
Foreign exchange impact and other	786
Non-U.S. Qualified Pension Plan
Change in projected benefit obligation
Benefits earned during the period	36	38
Interest cost on benefit obligation	71	73
Change in plan assets
Funded status of the Significant Plans	345
Non-U.S. Nonqualified Pension Plan
Change in plan assets
Funded status of the Significant Plans	0
U.S. Postretirement Benefit Plans
Change in projected benefit obligation
Projected benefit obligation at beginning of year	686
Projected benefit obligation at period end—Significant Plans	679
Change in plan assets
Plan assets at fair value at beginning of year	129
Plan assets at fair value at period end—Significant Plans	129
Funded status of the Significant Plans	(550)
Net amount recognized
Benefit asset	0
Benefit liability	(550)
Net amount recognized on the balance sheet—Significant Plans	(550)
Amounts recognized in AOCI
Prior service benefit	0
Net actuarial gain (loss)	104
Net amount recognized in equity-pretax	104
Accumulated benefit obligation at period end—Significant Plans	679
U.S. Postretirement Benefit Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation
Projected benefit obligation at beginning of year	0
Change in plan assets
Plan assets at fair value at beginning of year	0
U.S. Postretirement Benefit Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation
Projected benefit obligation at beginning of year	686
Benefits earned during the period	0
Interest cost on benefit obligation	6
Plan amendments	0
Actuarial loss	3
Benefits paid, net of participants’ contributions	(16)
Foreign exchange impact and other	0
Change in plan assets
Plan assets at fair value at beginning of year	129
Actual return on plan assets	4
Company contributions, net of reimbursements	12
Plan participants’ contributions	0
Benefits paid, net of government subsidy	(16)
Foreign exchange impact and other	0
U.S. Qualified Postretirement Benefit Plan
Change in projected benefit obligation
Benefits earned during the period	0	0
Interest cost on benefit obligation	6	8
Change in plan assets
Funded status of the Significant Plans	(550)
U.S. Nonqualified Postretirement Benefit Plan
Change in plan assets
Funded status of the Significant Plans	0
Non-U.S. Postretirement Benefit Plans
Change in projected benefit obligation
Projected benefit obligation at beginning of year	1,141
Projected benefit obligation at period end—Significant Plans	972
Change in plan assets
Plan assets at fair value at beginning of year	1,015
Plan assets at fair value at period end—Significant Plans	1,128
Funded status of the Significant Plans	156
Net amount recognized
Benefit asset	156
Benefit liability	0
Net amount recognized on the balance sheet—Significant Plans	156
Amounts recognized in AOCI
Prior service benefit	92
Net actuarial gain (loss)	(372)
Net amount recognized in equity-pretax	(280)
Accumulated benefit obligation at period end—Significant Plans	972
Non-U.S. Postretirement Benefit Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation
Projected benefit obligation at beginning of year	303
Change in plan assets
Plan assets at fair value at beginning of year	11
Non-U.S. Postretirement Benefit Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation
Projected benefit obligation at beginning of year	838
Benefits earned during the period	2
Interest cost on benefit obligation	20
Plan amendments	0
Actuarial loss	39
Benefits paid, net of participants’ contributions	(11)
Foreign exchange impact and other	84
Change in plan assets
Plan assets at fair value at beginning of year	1,004
Actual return on plan assets	36
Company contributions, net of reimbursements	0
Plan participants’ contributions	0
Benefits paid, net of government subsidy	(11)
Foreign exchange impact and other	99
Non-U.S. Qualified Postretirement Benefit Plan
Change in projected benefit obligation
Benefits earned during the period	2	3
Interest cost on benefit obligation	24	$ 24
Change in plan assets
Funded status of the Significant Plans	156
Non-U.S. Nonqualified Postretirement Benefit Plan
Change in plan assets
Funded status of the Significant Plans	$ 0