RETIREMENT BENEFITS - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Change in accumulated other comprehensive income (loss)
Balance, beginning of period			$ 226,143
Actuarial assumptions changes and plan experience	$ (213)		(721)
Net asset gain due to difference between actual and expected returns	123		419
Net amortization	59		171
Prior service cost	0		(5)
Curtailment/settlement gain	5		12
Foreign exchange impact and other	(19)		(141)
Change in deferred taxes, net	16		89
Change, net of tax	(29)	$ 12	(176)	$ (480)
Balance, end of period	228,622	232,690	228,622	232,690
Benefit plans
Change in accumulated other comprehensive income (loss)
Balance, beginning of period	(5,311)	(5,608)	(5,164)	(5,116)
Balance, end of period	$ (5,340)	$ (5,596)	$ (5,340)	$ (5,596)