Stock-Based Compensation - Nonvested Stock Award Activity (Details) - Restricted shares	3 Months Ended
	Oct. 31, 2016 $ / shares shares
Number of Shares
Nonvested stock awards at the beginning of the period (in shares) | shares	331,367
Granted (in shares) | shares	91,841
Cancelled (in shares) | shares	(2,238)
Vested (in shares) | shares	(188,163)
Nonvested stock awards at the end of the period (in shares) | shares	232,807
Weighted Average Fair Value
Nonvested stock awards at the beginning of the period (in dollars per share) | $ / shares	$ 46.09
Granted (in dollars per share) | $ / shares	78.05
Cancelled (in dollars per share) | $ / shares	55.09
Vested (in dollars per share) | $ / shares	41.61
Nonvested stock awards at the end of the period (in dollars per share) | $ / shares	$ 62.23