RETIREMENT BENEFITS - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Change in accumulated other comprehensive income (loss)
Change, net of tax	$ (465)	$ (90)
Pension Plans and Postretirement Benefit Plans
Change in accumulated other comprehensive income (loss)
Beginning-of-period balance, net of tax	(5,116)	$ (5,159)	$ (5,159)
Actuarial assumptions changes and plan experience	(875)		898
Net asset gain (loss) due to difference between actual and expected returns	163		(1,457)
Net amortizations	56		236
Prior service (cost) credit	30		(6)
Curtailment/settlement gain	1		57
Foreign exchange impact and other	(102)		291
Change in deferred taxes, net	262		24
Change, net of tax	(465)		43
End-of-period balance, net of tax	$ (5,581)		$ (5,116)