Note 13 - Treasury Stock and Repurchase Program (Details Textual) - USD ($)		1 Months Ended		12 Months Ended
		Jan. 30, 2012	Jan. 31, 2011	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016	Sep. 19, 2012
Treasury Stock, Shares, Acquired	[1]			20,045	44,924	52,907
Treasury Stock, Value, Acquired, Cost Method	[1]			$ 354,000	$ 741,000	$ 796,000
September 2012 Share Repurchase Program [Member]
Stock Repurchase Program, Authorized Amount							$ 3,000,000
Former Repurchase Program [Member]
Treasury Stock, Shares, Acquired		85,219
Treasury Stock, Value, Acquired, Cost Method		$ 1,036,000
January 2011 Share Repurchase Program [Member]
Treasury Stock, Shares, Acquired			18,400

[1] Were acquired during the $3 million repurchase program authorized in September 2012.