Note 4 - Earnings Per Share - Earnings Per Share (Details) - $ / shares	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Average common shares outstanding
Basic weighted-average number of common shares outstanding (in shares)	79,703,593	79,734,519
Dilutive effect of weighted-average outstanding common share equivalents
Diluted (in shares)	80,413,178	80,393,849
Average stock options and warrants with anti-dilutive effect (in shares)	19,900	359,544
Basic (in dollars per share)	$ 0.61	$ 0.58
Diluted (in dollars per share)	$ 0.61	$ 0.57
Warrant [Member]
Dilutive effect of weighted-average outstanding common share equivalents
Warrants (in shares)	416,607	452,368
Employee Stock Option [Member]
Dilutive effect of weighted-average outstanding common share equivalents
Warrants (in shares)	33,888	83,018
Restricted Stock Units (RSUs) [Member]
Dilutive effect of weighted-average outstanding common share equivalents
Warrants (in shares)	259,090	123,944

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