Note 15 - Income Taxes (Details Textual) - USD ($)		3 Months Ended		6 Months Ended			12 Months Ended
	Dec. 22, 2017	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2018
Unrecognized Tax Benefits		$ 200,000			$ 200,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense					0	$ 0
Income Tax Expense (Benefit)		614,681	$ 587,038		$ 1,111,449	$ 1,657,049
Effective Income Tax Rate Reconciliation, Repatriation Foreign Earnings, Foreign Cash and Certain Other Net Current Assets, Percent	15.50%
Effective Income Tax Rate Reconciliation, Repatriation Foreign Earnings, Remaining Income, Percent	8.00%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent					35.00%
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount		50,000
Foreign Earnings Repatriated		1,000,000
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability		$ 500,000
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member] | Earliest Tax Year [Member]
Open Tax Year					2013
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member] | Latest Tax Year [Member]
Open Tax Year					2017
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				21.00%			28.00%