Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018
Revenue from External Customer [Line Items]
Revenues	$ 1,502	$ 1,339	$ 2,518	$ 2,249
Small Business & Self-Employed
Revenue from External Customer [Line Items]
Revenues	833	713	1,741	1,532
Consumer
Revenue from External Customer [Line Items]
Revenues	461	416	551	490
Strategic Partner
Revenue from External Customer [Line Items]
Revenues	208	210	226	227
Online Ecosystem Subsegment | Small Business & Self-Employed
Revenue from External Customer [Line Items]
Revenues	394	285	765	547
Online Ecosystem Subsegment | Small Business & Self-Employed | QuickBooks
Revenue from External Customer [Line Items]
Revenues	231	168	448	317
Online Ecosystem Subsegment | Small Business & Self-Employed | Online Services
Revenue from External Customer [Line Items]
Revenues	163	117	317	230
Desktop Ecosystem Subsegment | Small Business & Self-Employed
Revenue from External Customer [Line Items]
Revenues	439	428	976	985
Desktop Ecosystem Subsegment | Small Business & Self-Employed | QuickBooks
Revenue from External Customer [Line Items]
Revenues	154	147	382	396
Desktop Ecosystem Subsegment | Small Business & Self-Employed | Desktop Services And Supplies
Revenue from External Customer [Line Items]
Revenues	285	281	594	589
Desktop Ecosystem Subsegment | Small Business & Self-Employed | QuickBooks Packaged Software
Revenue from External Customer [Line Items]
Revenues	$ 37	$ 40	$ 66	$ 70