Leases - Supplemental Cash Flow Information (Details) $ in Millions	9 Months Ended
	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating cash flows from operating leases	$ (287)
Operating cash flows from finance leases	(3)
Financing cash flows from finance leases	(17)
Right-of-use assets obtained in exchange for lease obligations: Operating leases	2,366
Right-of-use assets obtained in exchange for lease obligations: Finance leases	$ 163