Other Expense (Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Other Income and Expenses [Abstract]
Non-service cost components of net periodic pension expense (income)	$ 110	$ (658)	$ (182)
Foreign currency loss (gain)	14	(25)	31
Other gain	(22)	(37)	(155)
Totals	102	(720)	(306)
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ (537)	$ 252	$ (153)