Stock-Based Compensation - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Jul. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding unvested restricted stock shares	255,564		222,298
Outstanding options (in shares)	70,000		122,500
Total unrecognized stock-based compensation cost	$ 20,129
Remaining weighted average period for unrecognized compensation cost	26 months
Number of options exercised (in shares)	52,500
Deduction in income tax due to exercise of options and vesting of restricted stock	$ 4,125	$ 5,376
Reduction in income tax expense over the equity awards' vesting period	1,839	3,135
Excess tax benefit	$ 2,286	$ 2,241
2016 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding unvested restricted stock shares	206,289
Outstanding options (in shares)	0
Shares available under Plan	970,421
2006 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding unvested restricted stock shares	49,275
Outstanding options (in shares)	70,000
Employee and directors stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vested during period (in shares)	5,000
Aggregate fair value of all options vested	$ 132
Number of options exercised (in shares)	52,500
Aggregate fair value of exercised options	$ 4,049
Options granted in period (in shares)	0