Pension and Other Benefit Plans - Pension Plan, Amounts Recognized in Balance Sheet (Details) - Pension Plans, Defined Benefit - USD ($) $ in Millions	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Other assets	$ 1,735	$ 1,157
Accrued expenses and other current liabilities	(16)	(20)
Non-current pension obligations	(761)	(790)
Other long-term liabilities - OPEB	(18)	(20)
Net amount recorded	940	327
Accumulated benefit obligation	$ 10,072	$ 10,893