Note 5 - Goodwill and Intangible Assets (Details Textual)	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Business Acquisition Number of Acquisitions Resulting in Goodwill	5
Goodwill, Impairment Loss	$ 0		$ 0
Business Acquisition, Number of Acquisitions Resulting in Intangible Assets	3
Amortization of Intangible Assets, Total	$ 46,000	$ 69,000