Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (21)	$ 13	$ (38)	$ (17)
Other comprehensive income (loss), net of income taxes:
Unrealized losses on available-for-sale debt securities	(1)	0	(1)	(1)
Foreign currency translation gains (losses)	9	3	3	(1)
Total other comprehensive income (loss), net	8	3	2	(2)
Comprehensive income (loss)	$ (13)	$ 16	$ (36)	$ (19)