Note 10 - Stock-based Compensation (Details Textual) - USD ($)																		3 Months Ended		9 Months Ended
	Sep. 27, 2018	Apr. 20, 2018	Mar. 29, 2018	Mar. 28, 2018	Mar. 26, 2018	Mar. 22, 2018	Mar. 13, 2018	Mar. 08, 2018	Jan. 26, 2018	Jan. 08, 2018	Aug. 29, 2017	Aug. 14, 2017	Jul. 17, 2017	Jul. 06, 2017	May 23, 2017	May 08, 2017	Feb. 24, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	85,000	154,000	562,996	325,000	240,000	50,000	176,000	50,000	100,000	124,000	7,940		220,000	200,000	80,000	7,060		85,000	427,940	1,866,996	925,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross												1,280,000					535,000				1,815,000
Allocated Share-based Compensation Expense, Total																		$ 0	$ 675,941	$ 7,288	$ 161,590
Proceeds from Stock Options Exercised																		$ 98,715	$ 60,655	1,537,024	100,198
Stock Issued During Period, Value, Stock Options Exercised																				$ 1,537,024	$ 100,198
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate																	0.00%
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate																				0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Payments																				$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Estimated Forfeiture Rate																		0.00%	0.00%	0.00%	0.00%
Additional Paid-in Capital [Member]
Stock Issued During Period, Value, Stock Options Exercised																		$ (34,608)		$ (386,898)	$ (30,156)