Note 11 - Marketable Securities (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016	Jan. 01, 2018
Payments to Acquire Marketable Securities, Total	$ 63	$ 9,822		$ 2,466
Maximum [Member]
Held-to-maturity Securities, Debt Maturities, Period	5 years
Accounting Standards Update 2016-01 [Member] | Other Income, Net [Member]
Marketable Securities, Gain (Loss), Total	$ 3,500
Retained Earnings [Member] | Accounting Standards Update 2016-01 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ (1,136)	[1]		$ (1,100)

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