Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jan. 31, 2019
Number of shares
Outstanding, beginning balance (in shares)	70,000
Exercised (in shares)	(30,000)
Outstanding, ending balance (in shares)	40,000
Weighted Average Exercise Price
Outstanding, beginning balance (in dollars per share)	$ 38.60
Exercised (in dollars per share)	31.81
Outstanding, ending balance (in dollars per share)	$ 43.70
Stock Option Activity, Additional Disclosures
Options outstanding, Weighted average contractual life remaining (in years)	12 months 27 days
Options outstanding, Aggregate intrinsic value (in dollars)	$ 1,509
Options exercisable, number of options (in shares)	40,000
Options exercisable, Weighted average exercise price (in dollars per share)	$ 43.70
Options exercisable, Weighted average contractual life remaining (in years)	12 months 27 days
Options exercisable, Aggregate intrinsic value (in dollars)	$ 1,509