Stock-Based Compensation - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Jul. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding unvested restricted stock shares (in shares)	230,003		222,298
Outstanding options (in shares)	70,000		122,500
Total unrecognized stock-based compensation cost	$ 14,420
Remaining weighted average period for unrecognized compensation cost	20 months
Number of options exercised (in shares)	52,500
Options granted in period (in shares)	0
Deduction in income tax due to exercise of options and vesting of restricted stock	$ 3,406	$ 5,520
Reduction in income tax expense over the equity awards' vesting period	1,394	3,329
Excess tax benefit	$ 2,012	$ 2,191
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
2016 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding unvested restricted stock shares (in shares)	191,708
Outstanding options (in shares)	0
Shares available under Plan (in shares)	972,312
2006 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding unvested restricted stock shares (in shares)	38,295
Outstanding options (in shares)	70,000