Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash paid for amounts included in the measurement of:
Operating cash flows used in operating leases	$ 463	$ 506
Operating cash flows used in finance leases	35	50
Financing cash flows used in finance leases	$ 430	$ 436