Stock-Based Compensation - FV Assumptions and Option Activity (Details) - USD ($)	12 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Weighted-Average Black-Scholes Option Valuation Assumptions
Dividend yield (as a percent)	0.20%
Stock-based awards, additional disclosure
Deduction in income tax due to exercise of options and vesting of restricted stock (in dollars)	$ 3,059,000	$ 5,317,000
Increase in additional paid-in capital due to excess tax benefit on stock-based compensation expense (in dollars)	$ 1,179,000	$ 3,168,000
Stock options
Weighted-Average Black-Scholes Option Valuation Assumptions
Dividend yield (as a percent)	0.22%	0.25%
Expected volatility (as a percent)	55.90%	33.90%
Risk-free interest rate (as a percent)	1.41%	1.55%
Expected lives	5 years	5 years
Stock options, additional disclosure
Weighted average fair value of all options granted (in dollars per share)	$ 26.49	$ 11.54
Aggregate intrinsic value of all options exercised (in dollars)		$ 5,178,000	$ 5,702,000
Aggregate fair value of all options vested (in dollars)	$ 344,000	$ 248,000	$ 127,000
Number of Shares
Outstanding at the beginning of the period (in shares)	107,500	222,492	403,831
Granted (in shares)	15,000	25,000	30,000
Canceled (in shares)			(211,339)
Exercised (in shares)		(139,992)
Outstanding at the end of the period (in shares)	122,500	107,500	222,492
Exercisable at the end of the period (in shares)	80,834	45,000	157,492
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 25.73	$ 12.78	$ 8.25
Granted (in dollars per share)	55.36	36.70	31.81
Canceled (in dollars per share)			6.82
Exercised (in dollars per share)		7.11
Outstanding at the end of the period (in dollars per share)	29.36	25.73	12.78
Exercisable at the end of the period (in dollars per share)	$ 22.72	$ 20.32	$ 8.21
Aggregate intrinsic value of outstanding options (in dollars)	$ 4,605,000	$ 3,133,000