Revenue from Contracts with Customers 4 (Details) $ in Millions	3 Months Ended
	Jun. 30, 2018 USD ($)
Contract costs
Impairment loss on capitalized contract costs	$ 0
Selling and Marketing
Contract costs
Amortization of capitalized contract costs	$ 30
New Contracts
Contract costs
Capitalized contract costs, Amortization period	7 years
Renewal Contracts
Contract costs
Capitalized contract costs, Amortization period	3 years