Note 4 - Supplemental Cash Flow Information (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Taxes Paid			$ 5,220,000	$ 3,927,000
Interest Paid			$ 523,000	$ 512,000
Company Stock Received in Lieu of Cash Stock Options Exercised	0	2,164	43,841	12,598
Stock Issued During Period, Shares, New Issues	0	5,568	113,143	35,984