Quarterly Financial Data (Unaudited) (Tables)
 12 Months Ended
Dec. 31, 2014
Quarterly Financial Data [Abstract]  
Schedule of Quarterly Financial Information [Table Text Block]

  Year ended December 31, 2014 
   First Quarter   Second Quarter   Third Quarter   Fourth Quarter   Year 
Net sales $49,003  $50,154  $60,013  $102,415  $261,585 
Income (loss) from operations  1,940   1,580   (6,611)  20,074   16,983 
Net income (loss)  988   793   (4,319)  12,999   10,461 
Earnings (loss) per share attributable to stockholders: (1)                    
Basic $0.03  $0.03  $(0.14) $0.44  $0.35 
Diluted  0.03   0.03   (0.14)  0.43   0.34 
Weighted average common shares:                    
Basic  30,549   30,281   30,312   29,854   30,247 
Diluted  30,864   30,575   30,312   30,288   30,610 

 

 

 

  Year ended December 31, 2013 
   First Quarter   Second Quarter   Third Quarter   Fourth Quarter   Year 
Net sales $51,471  $51,198  $49,869  $66,818  $219,356 
Income (loss) from operations  2,007   5,416   6,435   (2,912)  10,946 
Net income (loss)  876   2,774   3,184   (2,044)  4,790 
Earnings (loss) per share attributable to stockholders: (1)                    
Basic $0.03  $0.09  $0.10  $(0.07) $0.16 
Diluted  0.03   0.09   0.10   (0.07)  0.15 
Weighted average common shares:                    
Basic  31,052   30,739   30,926   30,883   30,900 
Diluted  31,726   31,218   31,466   30,883   31,459 

 

   
(1) The earnings per share calculations for each of the quarters were based upon the weighted average number of shares outstanding during each period, and the sum of the quarters may not be equal to the full year earnings per common share amounts.