Note 1 - Nature of the Business and Summary of Significant Accounting Policies - Net Sales by Class of Retailer (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net sales	$ 84,522	$ 84,190	$ 79,980	$ 70,098	$ 65,752	$ 65,266	$ 60,052	$ 54,792	$ 51,643	$ 50,800	$ 47,625	$ 43,170	$ 318,790	$ 245,862	$ 193,237
Grocery (including Online), Mass and Club [Member]
Net sales													272,008	206,550	158,506
Pet Specialty and Natural [Member]
Net sales													$ 46,782	$ 39,312	$ 34,731