Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Details) - USD ($) $ in Millions	Apr. 30, 2016	Jul. 25, 2015
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	$ 10,396	$ 18,599
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(60)	(67)
Fair value of investment securities with unrealized losses12 months or greater	1,107	318
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(10)	(4)
Fair value of investment securities with unrealized losses	11,503	18,917
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(70)	(71)
Publicly traded equity securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	320	108
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(30)	(7)
Fair value of investment securities with unrealized losses12 months or greater	0	2
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair value of investment securities with unrealized losses	320	110
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(30)	(7)
Total fixed income securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	10,076	18,491
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(30)	(60)
Fair value of investment securities with unrealized losses12 months or greater	1,107	316
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(10)	(4)
Fair value of investment securities with unrealized losses	11,183	18,807
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(40)	(64)
Total fixed income securities | U.S. government securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	4,315	6,412
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3)	(6)
Fair value of investment securities with unrealized losses12 months or greater	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair value of investment securities with unrealized losses	4,315	6,412
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3)	(6)
Total fixed income securities | U.S. government agency securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	287	1,433
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(1)
Fair value of investment securities with unrealized losses12 months or greater	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair value of investment securities with unrealized losses	287	1,433
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	0	(1)
Total fixed income securities | Non-U.S. government and agency securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	192	515
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(1)
Fair value of investment securities with unrealized losses12 months or greater	0	4
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair value of investment securities with unrealized losses	192	519
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	0	(1)
Total fixed income securities | Corporate debt securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	5,145	9,552
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(27)	(49)
Fair value of investment securities with unrealized losses12 months or greater	1,089	312
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(10)	(4)
Fair value of investment securities with unrealized losses	6,234	9,864
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(37)	(53)
Total fixed income securities | U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	137	579
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(3)
Fair value of investment securities with unrealized losses12 months or greater	18	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair value of investment securities with unrealized losses	155	579
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 0	$ (3)