Stock-based Payment Compensation (Details) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jan. 31, 2020 USD ($) $ / shares shares	Jul. 31, 2019 USD ($) $ / shares shares
Shares
Outstanding as of July 31, 2019 | shares	14,552,000
Grants of options (in shares) | shares	150,000
Exercises (in shares) | shares	(5,852,000)
Forfeitures or expirations (in shares) | shares	(3,000)
Outstanding as of January 31, 2020 | shares	8,847,000	14,552,000
Exercisable as of January 31, 2020 | shares	5,315,000
Weighted Average Exercise Price
Outstanding as of July 31, 2019 | $ / shares	$ 26.29
Grants of options (in dollars per share) | $ / shares	88.58
Exercises (in dollars per share) | $ / shares	17.74
Forfeitures (in dollars per share) | $ / shares	(17.69)
Outstanding as of January 31, 2020 | $ / shares	33.01	$ 26.29
Exercisable as of January 31, 2020 | $ / shares	$ 23.53
Weighted Average Remaining Contractual Term (In years)
Outstanding as of July 31, 2019		6 years 14 days
Outstanding as of January 31, 2020	6 years 6 months 21 days
Exercisable as of January 31, 2020	5 years 6 months 10 days
Aggregate Intrinsic Value
Outstanding as of July 31, 2019 | $	$ 745,592
Outstanding as of January 31, 2020 | $	605,592	$ 745,592
Exercisable as of January 31, 2020 | $	$ 414,187
Restricted Shares
Outstanding as of July 31, 2019 | shares	134,000
Grants of restricted stock (in shares) | shares	69,000
Vested restricted stock (in shares) | shares	(3,000)
Forfeited restricted stock (in shares) | shares	(2,000)
Outstanding as of January 31, 2020 | shares	198,000	134,000
Outstanding as of July 31, 2019, Weighted Average Grant Date Fair Value | $ / shares	$ 56.62
Granted restricted stock, Weighted Average Grant Date Fair Value | $ / shares	82.33
Vested restricted stock, Weighted Average Grant Date Fair Value | $ / shares	47.18
Forfeited restricted stock, Weighted Average Grant Date Fair Value | $ / shares	63.07
Outstanding as of January 31, 2020, Weighted Average Grant Date Fair Value | $ / shares	$ 65.58	$ 56.62