Balance Sheet Details (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2017	[1]
Balance Sheet Related Disclosures [Abstract]
Depreciation expense	$ 30	$ 28	$ 59	$ 57
Deferred Revenue, Current	$ 1,116		$ 1,116		$ 1,539

[1] Derived from audited Consolidated Financial Statements.