RETIREMENT BENEFITS - Funded Status and Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
U.S. Pension Plans
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	$ 13,943
Projected benefit obligation at period end—Significant Plans	14,517
Change in plan assets
Plan assets at fair value at beginning of period	12,137
Company contributions	15	$ 11
Plan assets at fair value at period end—Significant Plans	12,065
Funded status of the Significant plans	(2,452)
Net amount recognized
Benefit asset	0
Benefit liability	(2,452)
Net amount recognized on the balance sheet—Significant Plans	(2,452)
Amounts recognized in Accumulated other comprehensive income (loss)
Prior service benefit	0
Net actuarial loss	(7,065)
Net amount recognized in equity-pretax	(7,065)
Accumulated benefit obligation at period end	14,506
U.S. Pension Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	0
Change in plan assets
Plan assets at fair value at beginning of period	0
U.S. Pension Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	13,943
Benefits earned during the period	2
Interest cost on benefit obligation	148
Plan amendments	0
Actuarial loss	632
Benefits paid, net of participants’ contributions	(208)
Foreign exchange impact and other	0
Change in plan assets
Plan assets at fair value at beginning of period	12,137
Actual return on plan assets	120
Company contributions	15
Plan participants’ contributions	0
Benefits paid, net of government subsidy	(207)
Foreign exchange impact and other	0
U.S. Nonqualified Pension Plan
Change in plan assets
Funded status of the Significant plans	(733)
Non-U.S. Pension Plans
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	6,534
Projected benefit obligation at period end—Significant Plans	4,914
Change in plan assets
Plan assets at fair value at beginning of period	6,104
Company contributions	32	26
Plan assets at fair value at period end—Significant Plans	5,162
Funded status of the Significant plans	248
Net amount recognized
Benefit asset	758
Benefit liability	(510)
Net amount recognized on the balance sheet—Significant Plans	248
Amounts recognized in Accumulated other comprehensive income (loss)
Prior service benefit	43
Net actuarial loss	(1,089)
Net amount recognized in equity-pretax	(1,046)
Accumulated benefit obligation at period end	4,618
Non-U.S. Pension Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	1,819
Change in plan assets
Plan assets at fair value at beginning of period	1,175
Non-U.S. Pension Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	4,715
Benefits earned during the period	22
Interest cost on benefit obligation	60
Plan amendments	(30)
Actuarial loss	196
Benefits paid, net of participants’ contributions	(55)
Foreign exchange impact and other	6
Change in plan assets
Plan assets at fair value at beginning of period	4,929
Actual return on plan assets	294
Company contributions	12
Plan participants’ contributions	1
Benefits paid, net of government subsidy	(55)
Foreign exchange impact and other	(19)
U.S. Postretirement Benefit Plans
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	817
Projected benefit obligation at period end—Significant Plans	839
Change in plan assets
Plan assets at fair value at beginning of period	166
Company contributions	14	20
Plan assets at fair value at period end—Significant Plans	166
Funded status of the Significant plans	(673)
Net amount recognized
Benefit asset	0
Benefit liability	(673)
Net amount recognized on the balance sheet—Significant Plans	(673)
Amounts recognized in Accumulated other comprehensive income (loss)
Prior service benefit	0
Net actuarial loss	(27)
Net amount recognized in equity-pretax	(27)
Accumulated benefit obligation at period end	839
U.S. Postretirement Benefit Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	0
Change in plan assets
Plan assets at fair value at beginning of period	0
U.S. Postretirement Benefit Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	817
Benefits earned during the period	0
Interest cost on benefit obligation	8
Plan amendments	0
Actuarial loss	30
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 period	166
Actual return on plan assets	2
Company contributions	14
Plan participants’ contributions	0
Benefits paid, net of government subsidy	(16)
Foreign exchange impact and other	0
Non-U.S. Postretirement Benefit Plans
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	1,291
Projected benefit obligation at period end—Significant Plans	1,039
Change in plan assets
Plan assets at fair value at beginning of period	1,133
Company contributions	2	$ 7
Plan assets at fair value at period end—Significant Plans	1,164
Funded status of the Significant plans	125
Net amount recognized
Benefit asset	125
Benefit liability	0
Net amount recognized on the balance sheet—Significant Plans	125
Amounts recognized in Accumulated other comprehensive income (loss)
Prior service benefit	109
Net actuarial loss	(478)
Net amount recognized in equity-pretax	(369)
Accumulated benefit obligation at period end	1,039
Non-U.S. Postretirement Benefit Plans | Other than Significant Plans Measured Annually
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	282
Change in plan assets
Plan assets at fair value at beginning of period	8
Non-U.S. Postretirement Benefit Plans | Significant Plans Measured Quarterly
Change in projected benefit obligation (PBO)
Projected benefit obligation at beginning of year	1,009
Benefits earned during the period	2
Interest cost on benefit obligation	20
Plan amendments	0
Actuarial loss	17
Benefits paid, net of participants’ contributions	(11)
Foreign exchange impact and other	2
Change in plan assets
Plan assets at fair value at beginning of period	1,125
Actual return on plan assets	48
Company contributions	0
Plan participants’ contributions	0
Benefits paid, net of government subsidy	(11)
Foreign exchange impact and other	$ 2