Description of Business and Summary of Significant Accounting Policies - Schedule of Impact of Topic 606 (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid expenses and other current assets	$ 184				$ 100				$ 184	$ 100
Long-term deferred income taxes	87				132				87	132
Other assets	190				143				190	143
Deferred revenue	961				887				961	887
Other current liabilities	191				178				191	178
Long-term deferred revenue	197				202				197	202
Other long-term obligations	123				130				123	130
Stockholders' equity	2,354				1,354				2,354	1,354	$ 1,161	$ 2,332
Net revenue	988	$ 2,925	$ 1,165	$ 886	842	$ 2,541	$ 1,016	$ 778	5,964	5,177	4,694
Cost of revenue									977	809
Selling and marketing									1,634	1,420	1,289
Operating income from continuing operations	$ (81)	$ 1,615	$ 20	$ (57)	$ (10)	$ 1,444	$ 22	$ (61)	1,497	1,395	1,242
Income tax provision									292	396	397
Net income from continuing operations									$ 1,211	$ 971	$ 806
Diluted net income per share (in dollars per share)	$ 0.18	$ 4.59	$ (0.08)	$ (0.07)	$ 0.09	$ 3.70	$ 0.05	$ (0.12)	$ 4.64	$ 3.72	$ 3.69
Pro Forma
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid expenses and other current assets	$ 202				$ 118				$ 202	$ 118
Long-term deferred income taxes	2				2				2	2
Other assets	213				164				213	164
Deferred revenue	581				574				581	574
Other current liabilities	198				185				198	185
Long-term deferred revenue	3				1				3	1
Other long-term obligations	184				201				184	201
Stockholders' equity	2,816				1,699				2,816	1,699
Net revenue									6,025	5,196
Cost of revenue									978	810
Selling and marketing									1,631	1,415
Operating income from continuing operations									1,560	1,418
Income tax provision									237	405
Net income from continuing operations									$ 1,329	$ 985
Diluted net income per share (in dollars per share)									$ 5.09	$ 3.78
Pro Forma | Accounting Standards Update 2014-09 | Topic 606 Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid expenses and other current assets	18				18				$ 18	$ 18
Long-term deferred income taxes	(85)				(130)				(85)	(130)
Other assets	23				21				23	21
Deferred revenue	(380)				(313)				(380)	(313)
Other current liabilities	7				7				7	7
Long-term deferred revenue	(194)				(201)				(194)	(201)
Other long-term obligations	61				71				61	71
Stockholders' equity	$ 462				$ 345				462	345
Net revenue									61	19
Cost of revenue									1	1
Selling and marketing									(3)	(5)
Operating income from continuing operations									63	23
Income tax provision									(55)	9
Net income from continuing operations									$ 118	$ 14
Diluted net income per share (in dollars per share)									$ 0.45	$ 0.06