Consolidated Statements of Comprehensive Income Statement - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 971	$ 979	$ 365
Other comprehensive income (loss), net of income taxes:
Unrealized gain (loss) on available-for-sale debt securities	(1)	1	(1)
Foreign currency translation gain (loss)	11	(3)	(27)
Total other comprehensive income (loss), net	10	(2)	(28)
Comprehensive income	$ 981	$ 977	$ 337