Revenues from Contracts with Customers Revenues from Contracts with Customers - Schedule of Contract Assets and Contract Liabilities (Details) - USD ($) $ in Millions	6 Months Ended
	Sep. 30, 2019	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Contract with Customer, Asset, Net	$ 1,031	$ 928
Billed trade receivables	2,679	2,690
Unbilled trade receivables	1,091	945
Contract with Customer, Liability	986	1,009
Sales commissions, opening balance	1,559
Sales commissions, additions	610
Capitalized Contract Cost, Amortization	(457)
Costs to acquire a customer contract	$ 1,712	$ 1,559