Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation (Details)

v3.2.0.727
Share-Based Compensation (Details)
$ / shares in Units, $ in Thousands
 6 Months Ended
Mar. 05, 2015
USD ($)
shares
Jun. 30, 2015
USD ($)
Percentile_Rank
$ / shares
shares
Jun. 30, 2014
shares
Options      
Exercised (in shares)   76,474 51,289
Performance share units      
Assumptions used to value stock awards      
Weighted average grant date fair value (in dollars per share) | $ / shares   $ 36.76  
Baseline value per common share (in dollars per share) | $ / shares   $ 29.28  
Expected volatility of common shares (as a percent)   19.90%  
Risk-free interest rate (as a percent)   0.99%  
Restricted shares      
Share-Based Compensation      
Stock awards granted (in shares or units)   184,074  
Aggregate grant date fair value | $   $ 5,400  
Assumptions used to value stock awards      
Weighted average grant date fair value (in dollars per share) | $ / shares   $ 29.35  
Other Share-based Compensation Additional Disclosures      
Shares vested (in shares)   149,787  
Weighted average fair value of shares vested (in dollars per share) | $ / shares   $ 25.96  
Aggregate intrinsic value of awards upon vesting | $   $ 4,300  
Deferred shares      
Share-Based Compensation      
Stock awards granted (in shares or units)   24,056  
Aggregate grant date fair value | $   $ 642  
Assumptions used to value stock awards      
Weighted average grant date fair value (in dollars per share) | $ / shares   $ 26.70  
Other Share-based Compensation Additional Disclosures      
Shares vested (in shares)   15,485  
Weighted average fair value of shares vested (in dollars per share) | $ / shares   $ 26.77  
Aggregate intrinsic value of awards upon vesting | $   $ 413  
Options      
Options      
Exercised (in shares)   76,474  
Weighted average exercise price (in dollars per share) | $ / shares   $ 26.27  
Aggregate intrinsic value of options exercised (in dollars) | $   $ 300  
2014 PSU Grants | Performance share units      
Share-Based Compensation      
Stock awards granted (in shares or units) 45,656    
Aggregate grant date fair value | $ $ 1,700    
Potential earned PSUs payout for defined levels of performance under awards      
Earned PSUs payout (as a percent of PSUs granted) on 75th or greater percentile rank   200.00%  
Earned PSUs payout (as a percent of PSUs granted) on 50th percentile rank   100.00%  
Earned PSUs payout (as a percent of PSUs granted) on 25th percentile rank   50.00%  
Performance share units granted on percentile rank below 25th (as a percent)   0.00%  
The number of percentile ranks to fall between to earn interpolated PSUs between such percentile ranks, conditioned on the percentile rank exceeding 25% | Percentile_Rank   2  
2012 PSU Grants | Performance share units      
Assumptions used to value stock awards      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Shares issued for Awards Vested in Period 40,309    
2013 PSU Grants | Performance share units | Former Chief Financial Officer      
Assumptions used to value stock awards      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Shares issued for Awards Vested in Period 15,289