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, 2018	Apr. 01, 2018	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract with Customer, Asset, Net	$ 687		$ 432
Billed trade receivables	2,751		2,559
Unbilled trade receivables	833		1,250
Contract with Customer, Liability	1,014		$ 1,104
Sales commissions, opening balance	1,219
Sales commissions, additions	550
Capitalized Contract Cost, Amortization	(390)
Costs to acquire a customer contract	1,379	$ 1,219
Revenue recognized from contract liability	$ 942