Note 9 - Marketable Securities (Details Textual) - Accounting Standards Update 2016-01 [Member] - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	[1]
Other Income, Net [Member]
Marketable Securities, Gain (Loss), Total	$ (100)
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ (1,100)	$ (1,136)

[1] Represents the impact of change in accounting principles for its respective Accounting Standard Updates ("ASU"). See Footnote 2 of the Notes to Condensed Consolidated Financial Statements for additional disclosure.