Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Detail) (USD $) In Millions, unless otherwise specified	Oct. 27, 2012	Jul. 28, 2012
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 13,216	$ 6,127
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(23)	(12)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		34
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		(3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	13,216	6,161
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(23)	(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	270	167
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(12)	(8)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		20
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		(3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	270	187
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(12)	(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	12,946	5,960
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(11)	(4)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		14
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	12,946	5,974
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(11)	(4)
Total Fixed Income Securities [Member] | U.S. Government Agency Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	12,477	5,357
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(9)	(1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	12,477	5,357
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(9)	(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	469	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		14
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	469	617
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$ (2)	$ (3)