Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Cash, FDIC Insured Amount	$ 250,000		$ 250,000
Cash, Uninsured Amount	4,827,512		4,827,512				$ 4,488,000
Depreciation	1,862,000	$ 1,669,000	3,744,000	$ 3,397,000
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Asset	0		$ 0
Standard Warranty Extended Term for Exceptions			10 years
Research and Development Expense	$ 1,379,000	$ 126,900	$ 2,941,000	$ 2,670,000
Incremental Common Shares Attributable to Dilutive Effect of Contingently Issuable Shares	756,000	787,000	686,000	852,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	28.90%	30.40%	28.90%	30.80%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 4,676,578
Income Tax Expense (Benefit)	$ 5,598,000	$ 832,000	$ (3,990,000)	$ 1,083,000
Accounting Standards Update 2016-09 [Member]
Income Tax Expense (Benefit)			$ 87,354
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent					21.00%	27.70%
Minimum [Member]
Media Content Service Period			30 days
Finite-Lived Intangible Asset, Useful Life			7 years
Standard Warranty Term			1 year
Maximum [Member]
Media Content Service Period			1 year
Finite-Lived Intangible Asset, Useful Life			20 years
Standard Warranty Term			5 years
Maximum [Member] | Leasehold Improvements [Member]
Property, Plant and Equipment, Useful Life			15 years