Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Retirement Benefits [Abstract]
Maximum percent of salary and bonus eligible for executive deferred compensation plan	75.00%
Executive deferred compensation plan liabilities	$ 108	$ 97
Maximum percent of pre tax salary eligible for contribution to employee plan	50.00%
Additional employer contribution for next six percent of salary (in percent)	125.00%
Additional salary contributed by the employee (in percent)	6.00%
Matching contributions	$ 59	$ 50	$ 49