Share-Based Compensation (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award    
Allocated Share-based Compensation Expense $ 2,707 $ 1,540
Excess Tax Benefit on Stock Plans 648 169
Restricted shares    
Share-based Compensation Arrangement by Share-based Payment Award    
Shares granted 15,080  
Weighted average grant date fair value, in dollars per share $ 66.97  
Vesting period of new awards granted 3 years  
Fair value of shares vested $ 811 $ 807