Note 9 - Dividends and Dividend Equivalents - Cash Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Dividend declared per share (in dollars per share)	$ 0.80	$ 0.80	$ 0.45
Total amount	$ 32,434	$ 31,618	$ 17,466