Income Taxes - Provision for income taxes from continuing operations (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Current:
Federal	$ 345	$ 401	$ 253
State	36	33	20
Foreign	8	13	7
Total current	389	447	280
Deferred:
Federal	4	(42)	14
State	1	(7)	1
Foreign	2	(1)	4
Total deferred	7	(50)	19
Total provision for income taxes from continuing operations	$ 396	$ 397	$ 299