Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Total net revenue	$ 754	$ 2,304	$ 923	$ 713	$ 696	$ 2,135	$ 749	$ 612	$ 4,694	$ 4,192	$ 4,243
Cost of revenue	171	216	199	166	176	202	188	159
All other costs and expenses	639	803	682	576	650	867	650	562
Operating income from continuing operations	(56)	1,285	42	(29)	(130)	1,066	(89)	(109)	1,242	738	1,300
Net income from continuing operations	(40)	848	29	(31)	(102)	656	(60)	(81)	806	413	853
Net income (loss) from discontinued operations	0	178	(5)	0	116	(155)	(6)	(3)	173	(48)	54
Net income	$ (40)	$ 1,026	$ 24	$ (31)	$ 14	$ 501	$ (66)	$ (84)	$ 979	$ 365	$ 907
Basic net income (loss) per share from continuing operations	$ (0.16)	$ 3.30	$ 0.11	$ (0.11)	$ (0.37)	$ 2.37	$ (0.21)	$ (0.28)	$ 3.08	$ 1.47	$ 2.99
Basic net income (loss) per share from discontinued operations	0.00	0.70	(0.02)	0.00	0.42	(0.56)	(0.02)	(0.01)	0.65	(0.17)	0.19
Basic net income per share	(0.16)	4.00	0.09	(0.11)	0.05	1.81	(0.23)	(0.29)	3.73	1.30	3.18
Diluted net income (loss) per share from continuing operations	(0.16)	3.26	0.11	(0.11)	(0.37)	2.33	(0.21)	(0.28)	3.04	1.45	2.94
Diluted net income (loss) per share from discontinued operations	0.00	0.68	(0.02)	0.00	0.42	(0.55)	(0.02)	(0.01)	0.65	(0.17)	0.18
Diluted net income per share	$ (0.16)	$ 3.94	$ 0.09	$ (0.11)	$ 0.05	$ 1.78	$ (0.23)	$ (0.29)	$ 3.69	$ 1.28	$ 3.12