Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Details) (USD $) In Millions, unless otherwise specified	Jan. 24, 2015	Jul. 26, 2014
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	$ 9,483	$ 10,044
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(37)	(26)
Fair value of investment securities with unrealized losses12 months or greater	364	558
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3)	(4)
Fair value of investment securities with unrealized losses	9,847	10,602
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(40)	(30)
Publicly traded equity securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	119	132
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(10)	(10)
Fair value of investment securities with unrealized losses12 months or greater	1	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	120	132
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(10)	(10)
Total fixed income securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	9,364	9,912
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(27)	(16)
Fair value of investment securities with unrealized losses12 months or greater	363	558
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3)	(4)
Fair value of investment securities with unrealized losses	9,727	10,470
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(30)	(20)
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	4,558	7,676
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1)	(12)
Fair value of investment securities with unrealized losses12 months or greater	0	45
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair value of investment securities with unrealized losses	4,558	7,721
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1)	(12)
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	854
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1)
Fair value of investment securities with unrealized losses12 months or greater	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Fair value of investment securities with unrealized losses	854
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(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		361
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(1)
Fair value of investment securities with unrealized losses12 months or greater		22
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Fair value of investment securities with unrealized losses		383
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		(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	3,952	1,875
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(25)	(3)
Fair value of investment securities with unrealized losses12 months or greater	363	491
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3)	(4)
Fair value of investment securities with unrealized losses	4,315	2,366
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (28)	$ (7)