XML 54 R42.htm IDEA: XBRL DOCUMENT v3.10.0.1
Note 6 - Stock-based Compensation (Details Textual) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance 0   0  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period     35,880 37,540
Proceeds from Stock Options Exercised     $ 838,000 $ 877,000
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price     $ 23.37  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value     $ 718,000 534,000
Benefit (Shortfall) of Tax Deductions from Share-based Compensation     $ 800,000 2,600,000
2005 Incentive Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant 2,591,461   2,591,461  
Restricted Stock Units (RSUs) [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period     3 years  
Allocated Share-based Compensation Expense, Total $ 1,900,000 $ 1,400,000 $ 3,400,000 2,600,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total $ 13,300,000 $ 10,600,000 $ 13,300,000 $ 10,600,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition     2 years 36 days 2 years 73 days
Performance-based Restricted Stock Units [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period     3 years