Stock-Based Compensation - Taxes (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Stock-based awards, additional disclosure
Deduction in income tax due to exercise of options and vesting of restricted stock (in dollars)	$ 169,000	$ 128,000	$ 5,545,000	$ 3,169,000
Income tax deductions previously recorded in income tax expense over the equity awards' vesting period	124,000	76,000	3,259,000	1,628,000
Increase in additional paid-in capital due to excess tax benefit on stock-based compensation expense		52,000		1,541,000
Reduction of income tax expense		$ 661,000		$ 1,274,000
ASU 2016-09 Share-Based Payment Accounting
Stock-based awards, additional disclosure
Reduction of income tax expense			2,286,000
New Accounting Pronouncement, Early Adoption, Effect | ASU 2016-09 Share-Based Payment Accounting
Stock-based awards, additional disclosure
Reduction of income tax expense	$ 45,000		$ 2,286,000