Pension and Other Benefit Plans - Amounts Recognized in Balance Sheet for Pension Plan Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2019	May 31, 2018
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Other assets		$ 7
Defined Benefit Pension Plan
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Other assets	$ 0
Other long-term liabilities	103
Retiree Medical Plan
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Other assets	6
Other long-term liabilities	$ 0