Quarterly report pursuant to Section 13 or 15(d)

Capital Transactions - Narrative (Details)

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Capital Transactions - Narrative (Details) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2015
Dec. 31, 2017
Dec. 31, 2012
2012 Stock Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Number of shares authorized under the plan (in shares)             1,500,000
Additional number of shares authorized under the plan (in shares)         1,500,000    
Maximum | 2009 Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Number of shares authorized under the plan (in shares) 400,000   400,000        
Time-based stock options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based compensation expense $ 100,000 $ (200,000) $ 200,000 $ 200,000      
Unrecognized share-based compensation expense $ 0   $ 0     $ 13,000  
Time-based stock options | 2012 Stock Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Granted (in shares)     50,000        
Exercised (in dollars per share)     $ 8.43        
Weighted-average grant date fair value (in dollars per share)     $ 3.30        
Expected contractual life (in years)     5 years        
Risk-free interest rate (as a percent)     2.80%        
Expected volatility (as a percent)     38.80%        
Time-based stock options | Maximum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting period     48 months        
Performance based stock options operating income margins              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Operating income margin, one (as a percent)     6.00%        
Operating income margin, two (as a percent)     8.00%        
Operating income margin, three (as a percent)     10.00%        
Stock options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Granted (in shares)     50,000        
Exercised (in dollars per share)     $ 6.10 $ 11.98      
Options outstanding (in shares) 1,114,000   1,114,000     1,390,000  
Aggregate intrinsic value, outstanding $ 300,000   $ 300,000     $ 900,000  
Exercisable (in shares)           1,293,000  
Expected to vest (in shares)           92,000  
Aggregate intrinsic value, exercisable           $ 900,000  
Aggregate intrinsic value, expected to vest           0  
Exercised (in shares)     99,000 9,000      
Aggregate intrinsic values of options exercised     $ 400,000 $ 200,000      
Tax benefit from the exercise of stock options     100,000 0      
RSUs              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based compensation expense 300,000 $ 300,000 1,300,000 1,700,000      
Unrecognized share-based compensation expense $ 2,400,000   $ 2,400,000     $ 2,000,000  
Discount for lack of marketability     11.90%        
Weighted-average period over which the remaining compensation cost is expected to be recognized     1 year 6 months        
Minimum withholding requirements (in shares)     55,000        
RSUs | 2012 Stock Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Granted (in shares)     511,000        
RSUs | Maximum | 2012 Stock Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting period     48 months        
RSUs | Minimum | 2012 Stock Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting period     12 months        
RSUs | Director | 2012 Stock Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Restriction period for issuance of shares     2 years        
Nonvested subject to restriction period (in shares) 71,000   71,000     96,000  
Performance-Based Restricted Stock Units (RSUs), Net Sales Growth Target | 2012 Stock Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting period     1 year        
Performance-Based Restricted Stock Units (RSUs), Earnings Per Share Achievement | 2012 Stock Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting period     1 year        
Earnings per share target period     45 days        
Performance-Based Restricted Stock Units (RSUs)              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based compensation expense     $ 0 $ 0      
Performance-Based Restricted Stock Units (RSUs) | 2012 Stock Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Weighted-average grant date fair value (in dollars per share)     $ 9.79        
Performance-Based Restricted Stock Units (RSUs) | Maximum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share based compensation potential compensation expense to be recognized $ 4,700,000   $ 4,700,000        
Performance-Based Restricted Stock Units (RSUs) | Net Sales and Operating Income Targets | 2012 Stock Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting period     3 years        
Time-Based Restricted Stock Units (RSUs) | 2012 Stock Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting period     3 years        
Weighted-average grant date fair value (in dollars per share)     $ 10.16