Note 11 - Treasury Stock and Repurchase Program (Details Textual) - USD ($)	1 Months Ended						3 Months Ended
	Jul. 31, 2018	Jun. 30, 2018	May 31, 2018	[1]	Jan. 30, 2012	Jan. 31, 2011	Jul. 31, 2018	Jul. 31, 2017	Sep. 19, 2012
Treasury Stock, Shares, Acquired			2,286
Treasury Stock, Value, Acquired, Cost Method			$ 46,000				$ 46,000	$ 40,000
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.