Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jan. 25, 2014	Jul. 27, 2013
Schedule of Investments [Line Items]
Available-for-sale Securities with Unrealized Losses Less than 12 Months, Fair Value	$ 5,972	$ 12,573
Gross Unrealized Losses, Less than 12 Months	(24)	(70)
Available-for-sale Securities with Unrealized Losses 12 Months or Longer, Fair Value	79	4
Gross Unrealized Losses, 12 Months or Longer	(1)	0
Available-for-sale Investments with Unrealized Losses, Fair Value	6,051	12,577
Total Gross Unrealized Losses	(25)	(70)
Publicly Traded Equity Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities with Unrealized Losses Less than 12 Months, Fair Value	61	278
Gross Unrealized Losses, Less than 12 Months	(4)	(4)
Available-for-sale Securities with Unrealized Losses 12 Months or Longer, Fair Value	0	0
Gross Unrealized Losses, 12 Months or Longer	0	0
Available-for-sale Investments with Unrealized Losses, Fair Value	61	278
Total Gross Unrealized Losses	(4)	(4)
Total Fixed Income Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities with Unrealized Losses Less than 12 Months, Fair Value	5,911	12,295
Gross Unrealized Losses, Less than 12 Months	(20)	(66)
Available-for-sale Securities with Unrealized Losses 12 Months or Longer, Fair Value	79	4
Gross Unrealized Losses, 12 Months or Longer	(1)	0
Available-for-sale Investments with Unrealized Losses, Fair Value	5,990	12,299
Total Gross Unrealized Losses	(21)	(66)
Total Fixed Income Securities [Member] | US Government Securities[Member]
Schedule of Investments [Line Items]
Available-for-sale Securities with Unrealized Losses Less than 12 Months, Fair Value	3,528	7,865
Gross Unrealized Losses, Less than 12 Months	(5)	(13)
Available-for-sale Securities with Unrealized Losses 12 Months or Longer, Fair Value	8	0
Gross Unrealized Losses, 12 Months or Longer	0	0
Available-for-sale Investments with Unrealized Losses, Fair Value	3,536	7,865
Total Gross Unrealized Losses	(5)	(13)
Total Fixed Income Securities [Member] | US Government Agencies Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities with Unrealized Losses Less than 12 Months, Fair Value	170	294
Gross Unrealized Losses, Less than 12 Months	0	(1)
Available-for-sale Securities with Unrealized Losses 12 Months or Longer, Fair Value	0	0
Gross Unrealized Losses, 12 Months or Longer	0	0
Available-for-sale Investments with Unrealized Losses, Fair Value	170	294
Total Gross Unrealized Losses	0	(1)
Total Fixed Income Securities [Member] | Non-US Government and Agency Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities with Unrealized Losses Less than 12 Months, Fair Value	294	432
Gross Unrealized Losses, Less than 12 Months	(1)	(2)
Available-for-sale Securities with Unrealized Losses 12 Months or Longer, Fair Value	2	0
Gross Unrealized Losses, 12 Months or Longer	0	0
Available-for-sale Investments with Unrealized Losses, Fair Value	296	432
Total Gross Unrealized Losses	(1)	(2)
Total Fixed Income Securities [Member] | Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities with Unrealized Losses Less than 12 Months, Fair Value	1,906	3,704
Gross Unrealized Losses, Less than 12 Months	(14)	(50)
Available-for-sale Securities with Unrealized Losses 12 Months or Longer, Fair Value	69	4
Gross Unrealized Losses, 12 Months or Longer	(1)	0
Available-for-sale Investments with Unrealized Losses, Fair Value	1,975	3,708
Total Gross Unrealized Losses	(15)	(50)
Total Fixed Income Securities [Member] | U.S. agency mortgage-backed Securities
Schedule of Investments [Line Items]
Available-for-sale Securities with Unrealized Losses Less than 12 Months, Fair Value	13
Gross Unrealized Losses, Less than 12 Months	0
Available-for-sale Securities with Unrealized Losses 12 Months or Longer, Fair Value	0
Gross Unrealized Losses, 12 Months or Longer	0
Available-for-sale Investments with Unrealized Losses, Fair Value	13
Total Gross Unrealized Losses	$ 0