Quarterly report pursuant to Section 13 or 15(d)

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

v3.10.0.1
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, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation expense $ 2,417 $ 2,064 $ 4,678 $ 4,026
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     25.00%  
Percentage of Peer Group By Which Company Share Price Must Outperform Before Maximum Incremental Shares Are Issued     90.00%  
Expected Stock Price Volatility Rate     24.30% 24.70%
Weighted Average Risk Free Interest Rate     2.20% 1.40%
Outstanding and non-vested, beginning of period (in shares)     69  
Grants in Period     18  
Shares Forfeited in Period     (22)  
Outstanding and non-vested, end of period (in shares) 65   65  
Outstanding and non-vested, weighted-average grant date fair value, beginning of period     $ 58  
Grants in Period, Weighted Average Grant Date Fair Value     72  
Forfeited in Period, Weighted Average Grant Date Fair Value     67  
Outstanding and non-vested, weighted-average grant date fair value, end of period $ 58   $ 58  
Outstanding and non-vested, aggregate grant date fair value     $ 3,795  
Share-based compensation expense $ 307 257 642 $ 441
Tax benefit related to share-based expense     161 160
Unrecognized share-based compensation, net of estimated forfeitures $ 2,036 $ 2,135 $ 2,036 $ 2,135
Weighted average period over which unrecognized compensation will be recognized (years)     2 years 11 days