Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Oct. 31, 2017	Oct. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (17)	$ (30)
Other comprehensive income (loss), net of income taxes:
Unrealized losses on available-for-sale debt securities	0	(1)
Foreign currency translation losses	(6)	(4)
Total other comprehensive income (loss), net	(6)	(5)
Comprehensive loss	$ (23)	$ (35)