Stockholder's Equity (Details 3) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended			12 Months Ended
	Jun. 12, 2020	Oct. 31, 2019	Apr. 30, 2019	Jan. 31, 2018	Jul. 31, 2020	Jul. 31, 2019
Number Of Options [Roll Forward]
Exercise of stock options, net of repurchased shares (in shares)		(4,000,000)	(3,000,000)	(80,000)
Weighted Average Exercise Price [Roll Forward]
Exercises (in dollars per share)		$ 17.81	$ 17.81	$ 6.54
Restricted Shares [Roll Forward]
Outstanding as of July 31,		134,000			134,000
Grants of restricted stock (in shares)					68,000
Vested restricted stock (in shares)					(74,000)
Forfeited restricted stock (in shares)					(23,000)
Outstanding as of July 31,					105,000	134,000
Outstanding as of July 31, Weighted Average Grant Date Fair Value		$ 56.62			$ 56.62
Granted restricted stock, Weighted Average Grant Date Fair Value					82.33
Vested restricted stock, Weighted Average Grant Date Fair Value					60.74
Forfeited restricted stock, Weighted Average Grant Date Fair Value					59.03
Outstanding as of July 31, Weighted Average Grant Date Fair Value					$ 69.86	$ 56.62
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights	106.30
Number of days threshold [Member]
Restricted Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights	20
Stock price increase threshold [Member]
Restricted Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights	125
Stock Options
Number Of Options [Roll Forward]
Outstanding at July 31, (in shares)		14,552,000			14,552,000
Grants of options (in shares)					1,175,000
Exercise of stock options, net of repurchased shares (in shares)					(7,461,000)
Forfeitures or expirations (in shares)					(207,000)
Outstanding at July 31, (in shares)					8,059,000	14,552,000
Exercisable as of July 31, 2019					4,756,000
Vested and expected to vest at July 31, 2019 (in shares)					7,758,000
Weighted Average Exercise Price [Roll Forward]
Outstanding at July 31, (in dollars per share)		$ 26.29			$ 26.29
Grants of options (in dollars per share)					85.45
Exercises (in dollars per share)					19.15
Forfeitures or expirations (in dollars per share)					29.95
Outstanding at July 31, (in dollars per share)					41.44	$ 26.29
Exercisable at July 31, 2020 (in dollars per share)					28.17
Vested and expected to vest at July 31, 2019 (in dollars per share)					$ 41.14
Weighted-Average Remaining Contractual Term [Roll Forward]
Outstanding at July 31,						6 years 14 days
Outstanding at July 31,					6 years 8 months 19 days
Exercisable at July 31, 2019					5 years 5 months 15 days
Vested and expected to vest at July 31, 2019					6 years 9 months 7 days
Aggregate Intrinsic Value [Roll Forward]
Outstanding at July 31,		$ 745,592			$ 745,592
Outstanding at July 31,					417,529	$ 745,592
Exercisable at July 31, 2019					309,493
Vested and expected to vest at July 31, 2020					$ 404,240