Acquisitions 3 (Details) € in Millions, $ in Millions						2 Months Ended	9 Months Ended	12 Months Ended
		Mar. 31, 2017 USD ($)	Jan. 18, 2017 EUR (€)	Jan. 18, 2017 USD ($)	Jul. 08, 2015 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)
Business Combinations [Abstract]
Accrued acquisition-related costs related to purchase price amounts withheld subject to indemnification protections		$ 12				$ 12		$ 11	$ 12
Business Acquisition
Purchase accounting adjustments for additional deferred tax assets	[1]							(105)
Total revenue								4,235	4,036	$ 4,025
Net income (loss)								476	$ 775	783
Automic
Business Acquisition
Percentage of voting equity interest / outstanding shares of common stock acquired			100.00%	100.00%
Payments to acquire businesses			€ 630	$ 675
Total revenue						25
Net income (loss)						$ (2)
Veracode
Business Acquisition
Percentage of voting equity interest / outstanding shares of common stock acquired		100.00%				100.00%			100.00%
Payments to acquire businesses		$ 618
Purchase accounting adjustments for additional deferred tax assets								(63)
Automic and Veracode
Business Acquisition
Total revenue								218
Net income (loss)								$ (66)
Fiscal Year 2017 Acquisitions | General and Administrative
Business Acquisition
Acquisition transaction costs									$ 10
Rally
Business Acquisition
Percentage of voting equity interest / outstanding shares of common stock acquired					100.00%
Payments to acquire businesses					$ 519
Rally and Xceedium
Business Acquisition
Total revenue							$ 97
Net income (loss)							$ (33)
Fiscal Year 2016 Acquisitions | General and Administrative
Business Acquisition
Acquisition transaction costs										$ 20

[1] Acquisitions amount relates to purchase price allocation adjustments that occurred during fiscal year 2018.