Note 7 - Segment Information - Net Sales for Geographic Areas (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net sales	$ 19,280,770	$ 19,522,905	$ 39,430,615	$ 40,195,132
UNITED STATES
Net sales	16,546,075	16,610,634	33,828,738	34,338,263
CANADA
Net sales	1,646,224	1,746,547	3,419,734	3,488,303
All Other Countries [Member]
Net sales	$ 1,088,471	$ 1,165,724	$ 2,182,143	$ 2,368,566