Overview and Summary of Significant Accounting Policies - Cumulative Impact of Adoption ASC 606 (Details) - USD ($) $ in Millions	Mar. 31, 2019	Apr. 01, 2018	Mar. 31, 2018
Item Effected [Line Items]
Impact of adoption of new accounting standard			$ 4
Assets:
Receivables, net	$ 484		354
Deferred contract costs	35		21
Other assets	192		21
Liabilities and Stockholders’ Equity:
Deferred revenue and advance contract payments	33	$ 27	53
Deferred tax liabilities	171		176
Other long-term liabilities	271		25
Total stockholders’ equity	2,162		$ 2,729
Balances Without Adoption of ASC 606
Assets:
Receivables, net	515
Deferred contract costs	31
Other assets	184
Liabilities and Stockholders’ Equity:
Deferred revenue and advance contract payments	56
Deferred tax liabilities	167
Other long-term liabilities	279
Total stockholders’ equity	2,154
Cumulative impact of ASC 606
Item Effected [Line Items]
Impact of adoption of new accounting standard		$ 4
Cumulative impact of ASC 606 | Effect of Change Higher/(Lower)
Assets:
Receivables, net	(31)
Deferred contract costs	4
Other assets	8
Liabilities and Stockholders’ Equity:
Deferred revenue and advance contract payments	(23)
Deferred tax liabilities	4
Other long-term liabilities	(8)
Total stockholders’ equity	$ 8