Note 2 - Adoption of New Accounting Standard (Details Textual)	6 Months Ended	9 Months Ended
	Jun. 30, 2018	Sep. 30, 2018 USD ($)	Jan. 01, 2018 USD ($)
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 485,000
Number of Reportable Segments	4	4
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 485,000
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption			$ 485,000