Earnings Per Common Share - Computation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Apr. 30, 2020	Apr. 30, 2019
Numerator for basic and diluted earnings per share:
Net income	$ 15,787	$ (2,263)	$ 5,767	$ 8,175	$ 18,800	$ 19,242	$ 19,291	$ 46,217
Less income allocated to participating securities	0			(5)			(3)	(51)
Net income available to common shareholders	$ 15,787			$ 8,170			$ 19,288	$ 46,166
Denominator for basic and diluted earnings per share, adjusted for participating securities:
Denominator for basic earnings per share - weighted average number of shares outstanding attributable to common stock (in shares)	42,187,539			41,720,733			42,266,677	41,685,623
Dilutive effect of stock awards using the treasury stock method and the average market price for the year (in shares)	0			38,705			60,858	40,608
Denominator for diluted earnings per share - weighted average number of shares and common stock equivalents attributable to common stock (in shares)	42,187,539			41,759,438			42,327,535	41,726,231
Earnings per share attributable to common stock:
Basic earnings per share (in dollars per share)	$ 0.37			$ 0.20			$ 0.46	$ 1.11
Diluted earnings per share (in dollars per share)	$ 0.37			$ 0.20			$ 0.46	$ 1.11
Stock awards excluded because their inclusion would have been anti-dilutive (in shares)	15,000			0			0	0