Note 11 - Segment Information - Net Sales for Geographic Areas (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net sales	$ 24,744,403	$ 18,887,099	$ 19,177,767	$ 20,288,918	$ 24,502,272	$ 18,388,381	$ 19,280,770	$ 20,149,845	$ 83,098,187	$ 82,321,268	$ 82,923,992
UNITED STATES
Net sales									71,443,246	70,453,773	70,886,401
CANADA
Net sales									7,120,452	7,224,894	7,199,155
All Other Countries [Member]
Net sales									$ 4,534,489	$ 4,642,601	$ 4,838,436