Stock-Based Compensation - Stock Option Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Apr. 30, 2018 USD ($) $ / shares shares
Number of shares
Outstanding at July 31, 2017 (in shares) | shares	122,500
Granted (in shares) | shares	0
Exercised (in shares) | shares	(52,500)
Outstanding at April 30, 2018 (in shares) | shares	70,000
Weighted Average Exercise Price
Outstanding at July 31, 2017 (in dollars per share) | $ / shares	$ 29.36
Granted (in dollars per share) | $ / shares	0.00
Exercised (in dollars per share) | $ / shares	17.04
Outstanding at April 30, 2018 (in dollars per share) | $ / shares	$ 38.60
Stock Option Activity, Additional Disclosures
Options outstanding, Weighted average contractual life remaining (in years)	1 year 2 months 12 days
Options outstanding, Aggregate intrinsic value (in dollars) | $	$ 5,143
Options exercisable, number of options (in shares) | shares	65,000
Options exercisable, Weighted average exercise price (in dollars per share) | $ / shares	$ 37.31
Options exercisable, Weighted average contractual life remaining (in years)	1 year 1 month 9 days
Options exercisable, Aggregate intrinsic value (in dollars) | $	$ 4,859