Quarterly report pursuant to Section 13 or 15(d)

Share-Based Payments - Non-employee Director Non-vested Shares (Details)

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Share-Based Payments - Non-employee Director Non-vested Shares (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Non-Employee Director Shares, Vesting Period (in years)     1 year  
Share-based compensation expense $ 1,939 $ 2,093 $ 5,965 $ 6,204
Nonemployee Director Nonvested Shares Granted Member        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Outstanding and non-vested, beginning of period (in shares) 10   16  
Grants in Period 4   14  
Shares Vested in Period 0   (16)  
Shares Forfeited in Period (1)   (1)  
Outstanding and non-vested, end of period (in shares) 13   13  
Outstanding and non-vested, weighted-average grant date fair value, beginning of period $ 51   $ 44  
Grants in Period, Weighted Average Grant Date Fair Value 54   52  
Vested in Period, Weighed-average grant date fair value 0   44  
Forfeited in Period, Weighted Average Grant Date Fair Value 51   51  
Outstanding and non-vested, weighted-average grant date fair value, end of period $ 52   $ 52  
Outstanding and non-vested, aggregate grant date fair value $ 656   $ 656  
Share-based compensation expense 153 173 470 555
Tax benefit related to share-based expense 54 64 167 198
Unrecognized share-based compensation, net of estimated forfeitures $ 430 $ 419 $ 430 $ 419
Weighted average period over which unrecognized compensation will be recognized (years) 7 months 11 days   7 months 11 days