Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Total net revenue	$ 1,816	$ 3,002	$ 1,696	$ 1,165	$ 994	$ 3,272	$ 1,502	$ 1,016	$ 7,679	$ 6,784	$ 6,025
Cost of revenue	322	426	340	290	281	354	285	247
All other costs and expenses	1,011	1,163	1,086	865	866	1,134	984	779
Operating income	483	1,413	270	10	(153)	1,784	233	(10)	2,176	1,854	1,560
Net income	$ 445	$ 1,084	$ 240	$ 57	$ (44)	$ 1,378	$ 189	$ 34	$ 1,826	$ 1,557	$ 1,329
Basic net income (loss) per share (in dollars per share)	$ 1.70	$ 4.15	$ 0.92	$ 0.22	$ (0.17)	$ 5.30	$ 0.73	$ 0.13	$ 6.99	$ 5.99	$ 5.18
Diluted net income (loss) per share (in dollars per share)	$ 1.68	$ 4.11	$ 0.91	$ 0.22	$ (0.17)	$ 5.22	$ 0.72	$ 0.13	$ 6.92	$ 5.89	$ 5.09