Note 2 - Supplemental Cash Flow Disclosure - Supplemental Disclosures of Cash Flow Information and Non-cash Investing and Financing Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest, net of interest capitalized	$ 717	$ 286	$ 1,843
Income taxes	29,144	3,023	2,793
Non-cash investing and financing activities:
Unrealized holding gains (losses) on marketable securities, net of tax	$ 6,356	$ 5,260	$ (1,120)