Note 11 - Treasury Stock and Repurchase Program (Details Textual) - USD ($)	1 Months Ended		3 Months Ended			9 Months Ended
	Jan. 30, 2012	Jan. 31, 2011	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Sep. 19, 2012
Treasury Stock, Shares, Acquired			2,285	6,512	2,353
Treasury Stock, Value, Acquired, Cost Method			$ 41,000	$ 110,000	$ 40,000	$ 191,000	$ 681,000
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