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Financial Instruments - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Oct. 30, 2015
Oct. 24, 2014
Oct. 30, 2015
Oct. 24, 2014
Apr. 24, 2015
Schedule of Investments [Line Items]          
Marketable securities $ 14,972   $ 14,972   $ 14,746
Cost 484   484   520
Other expense, net [Member]          
Schedule of Investments [Line Items]          
Impairment, cost method investments 19 $ 13 21 $ 13  
Other assets [Member]          
Schedule of Investments [Line Items]          
Marketable securities 202   202   186
Cost 484   484   520
Debt securities [Member]          
Schedule of Investments [Line Items]          
Credit loss portion of other-than-temporary impairments 0   0   0
Reductions for available-for-sale securities sold 0 0 0 0  
Other-than-temporary impairment losses on available-for-sale securities 0 0 0 0  
Marketable equity securities [Member] | Other expense, net [Member]          
Schedule of Investments [Line Items]          
Impairment charges, marketable securities 0 $ 7 20 $ 7  
Marketable equity securities [Member] | Other assets [Member]          
Schedule of Investments [Line Items]          
Marketable securities $ 99   $ 99   $ 80