PENSION AND POSTRETIREMENT BENEFIT PLANS (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Pension, Postretirement And Postemployment Liabilities Statement [Line Items]
Defined Benefit Plan Principal Pension Plan Assets Percentage		66.00%
Defined Benefit Plan Principal Pension Plan Obligations Percentage		60.00%
Net periodic benefit cost/(credit)		$ 44	$ (11)
Non-current pension liabilities		423		$ 427
Defined contribution plan expense		40	40
Pension Benefits [Member]
Pension, Postretirement And Postemployment Liabilities Statement [Line Items]
Service cost - benefits earned during the period		7	7
Interest cost on projected benefit obligation		44	46
Expected return on plan assets		(64)	(109)
Amortization of prior service credits		(1)	(1)
Amortization of net actuarial (gain)/loss		18	21
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment		49	31
Net periodic benefit cost/(credit)		$ 53	$ (5)
Bristol-Myers Squibb Retirement Income Plan [Member]
Pension, Postretirement And Postemployment Liabilities Statement [Line Items]
Defined Benefit Plan, Benefit Obligation				$ 3,700
Scenario, Forecast [Member] | Minimum [Member]
Pension, Postretirement And Postemployment Liabilities Statement [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	$ 1,500
Scenario, Forecast [Member] | Maximum [Member]
Pension, Postretirement And Postemployment Liabilities Statement [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	$ 2,000