Note 11 - Income Taxes - Summary of Changes in Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Balance	$ 47,606	$ 56,503	$ 46,453
Increases based on tax positions related to the current year	5,747	4,656	5,450
Increases based on tax positions of prior year	708
Decreases based on tax positions of prior year		(13,452)	(1,766)
Gross increases for acquired unrecognized tax benefits			6,585
Statute of limitation expirations	(118)	(101)	(219)
Balance	$ 53,943	$ 47,606	$ 56,503

Amount of unrecognized tax benefits.

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