Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Details) - USD ($) $ in Millions	Oct. 24, 2015	Jul. 25, 2015
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	$ 10,304	$ 18,599
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(78)	(67)
Fair value of investment securities with unrealized losses12 months or greater	1,060	318
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(13)	(4)
Fair value of investment securities with unrealized losses	11,364	18,917
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(91)	(71)
Publicly traded equity securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	103	108
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(11)	(7)
Fair value of investment securities with unrealized losses12 months or greater	2	2
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1)	0
Fair value of investment securities with unrealized losses	105	110
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(12)	(7)
Total fixed income securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	10,201	18,491
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(67)	(60)
Fair value of investment securities with unrealized losses12 months or greater	1,058	316
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(12)	(4)
Fair value of investment securities with unrealized losses	11,259	18,807
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(79)	(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	2,566	6,412
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1)	(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	2,566	6,412
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1)	(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	80	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	80	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	57	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	10	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	67	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	7,421	9,552
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(66)	(49)
Fair value of investment securities with unrealized losses12 months or greater	1,048	312
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(12)	(4)
Fair value of investment securities with unrealized losses	8,469	9,864
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(78)	(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	77	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	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	77	579
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 0	$ (3)