RETIREMENT BENEFITS - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Change in accumulated other comprehensive income (loss)
Balance, beginning of period				$ 193,946
Actuarial assumptions changes and plan experience		$ (1,230)		(800)
Net asset gain (loss) due to difference between actual and expected returns		1,106		(22)
Net amortization		72		148
Prior service cost		16		16
Curtailment/settlement gain		3		3
Foreign exchange impact and other		(60)		144
Change in deferred taxes, net		16		148
Change, net of tax	[1]	(77)	$ (253)	(363)	$ (317)
Balance, end of period		192,302	198,110	192,302	198,110
Benefit plans
Change in accumulated other comprehensive income (loss)
Balance, beginning of period		(7,095)	(6,321)	(6,809)	(6,257)
Balance, end of period		$ (7,172)	$ (6,574)	$ (7,172)	$ (6,574)

[1] See Note 17 to the Consolidated Financial Statements.