Fair Value Measurements (Financial Assets Measured At Fair Value On A Recurring and Nonrecurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended
	Oct. 31, 2015	Nov. 01, 2014
Impairment of Long-Lived Assets Held-for-use	$ 111
Carrying Value Of Long Lived Assets Held And Used	150
Long-lived assets held and used	39
Marketable equity and debt securities	98	$ 94
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Long-lived assets held and used	0
Marketable equity and debt securities	0	0
Significant Observable Inputs (Level 2) [Member]
Long-lived assets held and used	0
Marketable equity and debt securities	98	94
Significant Unobservable Inputs (Level 3) [Member]
Long-lived assets held and used	39
Marketable equity and debt securities	$ 0	$ 0