Note 7 - Pledged Assets, Notes Payable and Long-Term Debt (Details) - Long-term Debt (USD $) In Thousands, unless otherwise specified	Jul. 31, 2013	Apr. 30, 2013
Long-term Debt [Abstract]
Industrial Revenue Bonds, Series 2006A, 5-year adjustable interest rate based on the yield on 5-year United States Treasury Notes, plus .45% (1.89% as of January 31, 2013), due in monthly principal and interest payments beginning October 1, 2006 through maturity on September 1, 2026, secured by real estate. Effective September 1, 2011, the 5-year adjustable interest rate was reset to 1.89% for the next five years.	$ 2,758	$ 2,804
Operating line of credit, $6,000,000 limit on borrowing capacity, prime rate (3.25% at July 31, 2013) plus/minus 0.5% performance based interest, due in full on October 30, 2014, secured by accounts receivable and inventory. The interest rate as of July 31, 2013 was 2.75%	0	0
	2,758	2,804
Less current maturities	186	185
Total long-term debt	$ 2,572	$ 2,619