Quarterly report pursuant to Section 13 or 15(d)

Share-Based Payments - Employee Activity Performance Shares (Details)

v3.5.0.2
Share-Based Payments - Employee Activity Performance Shares (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation expense $ 2,159 $ 1,890 $ 4,111 $ 3,676
Key Employee Performance Share Based Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Period of Share Price Performance Comparison to Peer Group     3 years  
Minimum percentage of peer group by which Company share price must outperform before incremental performance shares are issued     30.00%  
Percentage of Peer Group By Which Company Share Price Must Outperform Before Maximum Incremental Shares Are Issued     90.00%  
Expected Stock Price Volatility Rate     22.30% 23.50%
Weighted Average Risk Free Interest Rate     0.80% 1.00%
Outstanding and non-vested, beginning of period (in shares) 80   77  
Grants in Period 0   29  
Additional Shares Awarded Based on Performance, Shares Issued in Period 0   7  
Shares Vested in Period 0   (33)  
Outstanding and non-vested, end of period (in shares) 80   80  
Outstanding and non-vested, weighted-average grant date fair value, beginning of period $ 55   $ 52  
Grants in Period, Weighted Average Grant Date Fair Value 0   49  
Stock Issued During Period, Weighted Average Grant Date Fair Value 0   40  
Vested in Period, Weighed-average grant date fair value 0   40  
Outstanding and non-vested, weighted-average grant date fair value, end of period $ 55   $ 55  
Outstanding and non-vested, aggregate grant date fair value $ 4,373   $ 4,373  
Share-based compensation expense 363 333 714 $ 635
Tax benefit related to share-based expense 135 128 266 244
Unrecognized share-based compensation, net of estimated forfeitures $ 2,442 $ 2,399 $ 2,442 $ 2,399
Weighted average period over which unrecognized compensation will be recognized (years) 2 years 11 days   2 years 11 days