Royalties And Licenses (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended 90 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 31, 2022
Royalties And Licenses [Line Items]      
Royalty Related Loss And Or Impairment Charges $ 122 $ 35  
Expected accretion expense     29
Unrecorded unconditional purchase obligation 2,165    
Developer/Licensor Commitments      
Royalties And Licenses [Line Items]      
Unrecorded unconditional purchase obligation 1,584    
Unrecognized Royalty-Based Commitment Losses [Member]      
Royalties And Licenses [Line Items]      
Loss on Contract Termination   18  
Royalty-Based Asset Losses [Member]      
Royalties And Licenses [Line Items]      
Loss on Contract Termination   $ 17