Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Detail) (USD $) In Millions, unless otherwise specified	Jan. 26, 2013	Jul. 28, 2012
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 3,667	$ 6,127
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(7)	(12)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	34
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	(3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,667	6,161
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(7)	(15)
Publicly Traded Equity Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	36	167
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(4)	(8)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	20
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	(3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	36	187
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(4)	(11)
Total Fixed Income Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	3,631	5,960
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(3)	(4)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	14
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,631	5,974
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(3)	(4)
Total Fixed Income Securities [Member] | US Treasury and Government [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	2,617	5,357
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(1)	(1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,617	5,357
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(1)	(1)
Total Fixed Income Securities [Member] | Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,014	603
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(2)	(3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	14
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,014	617
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$ (2)	$ (3)