Note N - Quarterly Results of Operations (unaudited) (Details) - Quarterly Results of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Note N - Quarterly Results of Operations (unaudited) (Details) - Quarterly Results of Operations [Line Items]
Revenues	$ 489,187	$ 464,676
Gross profit	183,185	176,756
Net income	21,129	32,165
Net income attributable to common	21,089	32,125
Earnings per share, basic (in Dollars per share)	$ 2.36	$ 3.53	$ 3.36
Earnings per share, diluted (in Dollars per share)	$ 2.25	$ 3.36	$ 3.24
First Quarter [Member]
Note N - Quarterly Results of Operations (unaudited) (Details) - Quarterly Results of Operations [Line Items]
Revenues	122,544	110,000
Gross profit	46,527	42,112
Net income	7,541	8,118
Net income attributable to common	7,531	8,108
Earnings per share, basic (in Dollars per share)	$ 0.83	$ 0.87
Earnings per share, diluted (in Dollars per share)	$ 0.79	$ 0.83
Second Quarter [Member]
Note N - Quarterly Results of Operations (unaudited) (Details) - Quarterly Results of Operations [Line Items]
Revenues	121,431	110,219
Gross profit	44,942	41,990
Net income	5,805	7,278
Net income attributable to common	5,795	7,268
Earnings per share, basic (in Dollars per share)	$ 0.64	$ 0.80
Earnings per share, diluted (in Dollars per share)	$ 0.61	$ 0.76
Third Quarter [Member]
Note N - Quarterly Results of Operations (unaudited) (Details) - Quarterly Results of Operations [Line Items]
Revenues	122,588	118,922
Gross profit	46,308	45,274
Net income	1,470	7,980
Net income attributable to common	1,460	7,970
Earnings per share, basic (in Dollars per share)	$ 0.16	$ 0.88
Earnings per share, diluted (in Dollars per share)	$ 0.16	$ 0.84
Fourth Quarter [Member]
Note N - Quarterly Results of Operations (unaudited) (Details) - Quarterly Results of Operations [Line Items]
Revenues	122,624	125,535
Gross profit	45,408	47,380
Net income	6,313	8,789
Net income attributable to common	$ 6,303	$ 8,779
Earnings per share, basic (in Dollars per share)	$ 0.72	$ 0.97
Earnings per share, diluted (in Dollars per share)	$ 0.68	$ 0.92