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Note 15 - Weighted-average Assumptions used in the Black-Scholes-Merton Option Pricing Model (Details) - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Weighted average grant date fair value (in dollars per share) $ 19.07 $ 26.35 $ 16.30
Expected stock price volatility 41.00% 45.00% 47.00%
Risk free interest rate 1.72% 1.90% 1.21%
Expected annual dividend per share (in dollars per share) $ 0 $ 0 $ 0
Expected life of options (years) 6 years 91 days 6 years 91 days 6 years 91 days