Investments (Maturities Of Fixed Income Securities) (Detail) (USD $) In Millions, unless otherwise specified	Jan. 25, 2014
Schedule of Investments [Line Items]
Fixed Income Securities, Amortized Cost	$ 39,640
Fixed Income Securities, Fair Value	39,731
Less than 1 year [Member]
Schedule of Investments [Line Items]
Fixed Income Securities, Amortized Cost	15,121
Fixed Income Securities, Fair Value	15,132
Fixed Income Securities Matures Between One And Two Years [Member]
Schedule of Investments [Line Items]
Fixed Income Securities, Amortized Cost	12,161
Fixed Income Securities, Fair Value	12,196
Fixed Income Securities Matures Between Two And Five Years [Member]
Schedule of Investments [Line Items]
Fixed Income Securities, Amortized Cost	11,634
Fixed Income Securities, Fair Value	11,673
Fixed Income Securities Matures Beyond Five Years [Member]
Schedule of Investments [Line Items]
Fixed Income Securities, Amortized Cost	724
Fixed Income Securities, Fair Value	$ 730