Consolidated Balance Sheets - Parenthetical - USD ($) $ in Millions	Jul. 31, 2017	Jul. 31, 2016
Allowance for doubtful accounts:	$ 46	$ 51
Preferred Stock:
Preferred Stock, Par Value (in dollars per share)	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized (in shares)	1,345,000	1,345,000
Preferred Stock, Shares Issued (in shares)	0	0
Preferred Stock, Shares Outstanding (in shares)	0	0
Common Stock:
Common Stock, Par Value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized (in shares)	750,000,000	750,000,000
Common Stock, Shares, Outstanding (in shares)	255,668,000	257,853,000
Series A Preferred Stock
Preferred Stock:
Preferred Stock, Shares Authorized (in shares)	145,000	145,000
Series B Preferred Stock
Preferred Stock:
Preferred Stock, Shares Authorized (in shares)	250,000	250,000