XML 69 R53.htm IDEA: XBRL DOCUMENT v3.8.0.1
Stock-Based Compensation - Additional Information (Details) - USD ($)
1 Months Ended 12 Months Ended 36 Months Ended
Apr. 22, 2008
Sep. 30, 2014
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Mar. 13, 2013
Feb. 29, 2008
Unvested Stock Options                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Amount of nonvested stock options (in shares)       0 0       0    
Restricted Stock Units                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Restricted stock units awarded (in shares)     22,000 4,020 12,589            
Stock-based compensation expense     $ 900,000 $ 900,000 $ 1,600,000            
Vested (in shares)     26,399 54,215 150,073            
Number of performance-based shares forfeited (in shares)     4,537 17,324 16,500            
Weighted average remaining recognition period of unrecognized stock-based compensation costs (in years)     2 years 1 month 6 days 2 years 9 months 18 days 3 years 9 months 18 days            
Performance Shares                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Restricted stock units awarded (in shares)     29,494 99,466   125,392          
Vesting period   3 years                  
Stock-based compensation expense     $ 1,300,000 $ 1,800,000 $ 1,300,000            
Vested (in shares)     61,919 84,417   6,915          
Number of performance-based shares forfeited (in shares)     11,770 29,423 24,056 24,056          
Weighted average remaining recognition period of unrecognized stock-based compensation costs (in years)     1 year 8 months 12 days                
Performance Shares | Maximum                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Unrecognized compensation costs related to unvested options     $ 7,300,000 $ 0       $ 7,300,000 $ 0    
Long-term incentive plan                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Maximum number of shares of common stock available for awards before amendment (in shares)                   2,175,000 2,000,000
Maximum number of shares of common stock available for awards (in shares)                   2,975,000 2,175,000
Plan expiration period (in years) 20 years                    
Shares remaining available for awards (in shares)     248,534         248,534      
Long-term incentive plan | Stock Options                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Granted (in shares)     0 0 0            
Stock-based compensation expense not recognized by employer     $ 0 $ 0 $ 0     $ 0 $ 0    
Executive Officer | Restricted Stock Units                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Restricted stock units awarded (in shares)       4,020 3,963            
Vesting period       5 years 3 years            
Executive Officer | Performance Shares                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Vesting period       3 years       3 years 3 years    
Stock-based compensation expense       $ 0   $ 100,000          
Shares recognized in period (in shares)       7,529              
Vested (in shares)     54,390 2,083   6,915     82,334    
Forecast | Performance Shares                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Vesting period             3 years