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								12 Months Ended
	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 17,348	$ 14,553	$ 17,637	$ 21,661	$ 13,372	$ 12,013	$ 18,180	$ 15,158	$ 71,199	$ 58,723	$ 35,499
Denominator for basic earnings per common share - weighted-average shares									16,259	16,256	15,764
Stock options and restricted stock units									139	186	273
Denominator for diluted earnings (loss) per common share - weighted-average shares and assumed conversions									16,398	16,442	16,037
Net earnings per share, Basic (usd per share)	$ 1.07	$ 0.90	$ 1.08	$ 1.33	$ 0.82	$ 0.74	$ 1.12	$ 0.94	$ 4.38	$ 3.61	$ 2.25
Net earnings per share, Diluted (usd per share)	$ 1.06	$ 0.89	$ 1.07	$ 1.32	$ 0.81	$ 0.73	$ 1.10	$ 0.92	$ 4.34	$ 3.57	$ 2.21