Earnings Per Share (Schedule Of Earnings (Loss) Per Share, Basic And Diluted) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						6 Months Ended	9 Months Ended	12 Months Ended
	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jul. 31, 2016	Oct. 31, 2016	Jan. 31, 2017	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 19,109	$ 1,996	$ 19,755	$ 22,281	$ 17,348	$ 21,661	$ 17,637	$ 14,553	$ 63,141	$ 71,199	$ 58,723
Denominator for basic earnings per common share - weighted-average shares									16,631	16,259	16,256
Stock options and restricted stock units									114	139	186
Denominator for diluted earnings (loss) per common share - weighted-average shares and assumed conversions									16,745	16,398	16,442
Net earnings per share, Basic (usd per share)	$ 1.09	$ 0.12	$ 1.22	$ 1.37	$ 1.07	$ 1.33	$ 1.08	$ 0.90	$ 3.80	$ 4.38	$ 3.61
Net earnings per share, Diluted (usd per share)	$ 1.08	$ 0.12	$ 1.21	$ 1.36	$ 1.06	$ 1.32	$ 1.07	$ 0.89	$ 3.77	$ 4.34	$ 3.57