Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Details) - USD ($) $ in Millions	Jan. 23, 2016	Jul. 25, 2015
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	$ 30,516	$ 18,599
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(218)	(67)
Fair value of investment securities with unrealized losses12 months or greater	1,274	318
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(23)	(4)
Fair value of investment securities with unrealized losses	31,790	18,917
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(241)	(71)
Publicly traded equity securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	694	108
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(62)	(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	696	110
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(63)	(7)
Total fixed income securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	29,822	18,491
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(156)	(60)
Fair value of investment securities with unrealized losses12 months or greater	1,272	316
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(22)	(4)
Fair value of investment securities with unrealized losses	31,094	18,807
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(178)	(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	15,432	6,412
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(16)	(6)
Fair value of investment securities with unrealized losses12 months or greater	3	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	15,435	6,412
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(16)	(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	1,793	1,433
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2)	(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	1,793	1,433
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2)	(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	645	515
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1)	(1)
Fair value of investment securities with unrealized losses12 months or greater	17	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	662	519
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(1)	(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	11,565	9,552
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(136)	(49)
Fair value of investment securities with unrealized losses12 months or greater	1,252	312
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(22)	(4)
Fair value of investment securities with unrealized losses	12,817	9,864
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(158)	(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	387	579
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1)	(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	387	579
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (1)	$ (3)