Acquisitions (Components of Intangible Assets Recognized) (Details) - USD ($) $ in Millions	Feb. 09, 2017	Aug. 01, 2016	Mar. 31, 2017
Blue Coat, Inc.
Business Acquisition [Line Items]
Total identified finite-lived intangible assets		$ 1,589
Indefinite lived assets acquired		19
Total identified intangible assets		1,608	$ 1,600
Blue Coat, Inc. | Customer relationships
Business Acquisition [Line Items]
Total identified finite-lived intangible assets		$ 844
Weighted-Average Estimated Useful Life		7 years
Blue Coat, Inc. | Developed technology and patents
Business Acquisition [Line Items]
Total identified finite-lived intangible assets		$ 739
Weighted-Average Estimated Useful Life		4 years 3 months 18 days
Blue Coat, Inc. | Finite-lived trade names
Business Acquisition [Line Items]
Total identified finite-lived intangible assets		$ 4
Weighted-Average Estimated Useful Life		2 years
Blue Coat, Inc. | Product backlog
Business Acquisition [Line Items]
Total identified finite-lived intangible assets		$ 2
Weighted-Average Estimated Useful Life		4 months
LifeLock
Business Acquisition [Line Items]
Total identified finite-lived intangible assets	$ 664
Indefinite lived assets acquired	583
Total identified intangible assets	1,247		$ 1,200
LifeLock | Customer relationships
Business Acquisition [Line Items]
Total identified finite-lived intangible assets	$ 532
Weighted-Average Estimated Useful Life	7 years
LifeLock | Developed technology and patents
Business Acquisition [Line Items]
Total identified finite-lived intangible assets	$ 126
Weighted-Average Estimated Useful Life	5 years
LifeLock | Finite-lived trade names
Business Acquisition [Line Items]
Total identified finite-lived intangible assets	$ 6
Weighted-Average Estimated Useful Life	5 years 10 months 25 days