Royalties And Licenses (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2015
Royalties And Licenses [Line Items]
Asset Impairment Charges	$ 23
Expected accretion expense through March 2022	15
Business Exit Costs	19	$ 122
Royalty-Based Asset Impairment Charge and Loss On Previously Minimum Unrecognized Royalty-Based Commitment	42
Developer And Licensor - Royalty Bearing [Member]
Royalties And Licenses [Line Items]
Unrecorded unconditional purchase obligation	1,140
Research and Development Expense
Royalties And Licenses [Line Items]
Asset Impairment Charges	32
Cost of service revenue [Member]
Royalties And Licenses [Line Items]
Business Exit Costs	$ 10