Goodwill and Intangible Assets (Schedule of Changes in the Carrying Amount of Goodwill) (Details) - USD ($)		6 Months Ended
		Sep. 30, 2016	Aug. 01, 2016
Goodwill [Roll Forward]
Net balance, beginning	[1]	$ 3,148,000,000
Acquisition of Blue Coat		4,086,000,000
Translation adjustments		(2,000,000)
Net balance, ending		7,232,000,000
Blue Coat, Inc.
Goodwill [Roll Forward]
Goodwill, expected tax deductible amount			$ 0
Consumer Security
Goodwill [Roll Forward]
Net balance, beginning		1,231,000,000
Acquisition of Blue Coat		0
Translation adjustments		0
Net balance, ending		1,231,000,000
Enterprise Security
Goodwill [Roll Forward]
Net balance, beginning		1,917,000,000
Acquisition of Blue Coat		4,086,000,000
Translation adjustments		(2,000,000)
Net balance, ending		$ 6,001,000,000

[1] Derived from audited financial statements.