Balance Sheet Details (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017	[1]
Balance Sheet Related Disclosures [Abstract]
Depreciation expense	$ 30	$ 29	$ 89	$ 86
Deferred Revenue, Current	$ 1,946		$ 1,946		$ 1,539

[1] Derived from audited Consolidated Financial Statements.