| Schedule of Segment Reporting Information, by Segment [Table Text Block] | 
     |     |    
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 |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |     |  
 |    |  $ |  81,386 |    |    |  $ |  78,521 |    |    |  $ |  232,984 |    |    |  $ |  229,347 |    |     |  
 |    |    |  29,929 |    |    |    |  20,001 |    |    |    |  76,013 |    |    |    |  56,417 |    |     |  
 |    |    |  19,693 |    |    |    |  15,669 |    |    |    |  55,327 |    |    |    |  49,061 |    |     |  
 |    |    |  (35 |   
 |    |    |  (33 |   
 |    |    |  (63 |   
 |    |    |  (242 |   
 |     |  
 |    |    |  130,973 |    |    |    |  114,158 |    |    |    |  364,261 |    |    |    |  334,583 |    |     |   |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |      Segment operating income:  
 |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |     |  
 |    |    |  45,133 |    |    |    |  44,620 |    |    |    |  124,436 |    |    |    |  122,967 |    |     |  
 |    |    |  9,454 |    |    |    |  6,186 |    |    |    |  21,464 |    |    |    |  17,422 |    |     |  
 |    |    |  1,592 |    |    |    |  (1,710 |   
 |    |    |  1,948 |    |    |    |  4,461 |    |     |  
 |    |    |  56,179 |    |    |    |  49,096 |    |    |    |  147,848 |    |    |    |  144,850 |    |     |   |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |      Costs recognized on sale of acquired inventory  
 |    |    |  (1,082 |   
 |    |    |  (897 |   
 |    |    |  (3,439 |   
 |    |    |  (5,252 |   
 |      Amortization of acquisition related intangible assets  
 |    |    |  (7,276 |   
 |    |    |  (6,751 |   
 |    |    |  (22,048 |   
 |    |    |  (19,337 |   
 |      Acquisition related expenses  
 |    |    |  (1,313 |   
 |    |    |  (335 |   
 |    |    |  (2,284 |   
 |    |    |  (3,906 |   
 |     |  
 |    |    |  (2,317 |   
 |    |    |  (1,288 |   
 |    |    |  (6,676 |   
 |    |    |  (4,725 |   
 |      Corporate general, selling, and administrative  
 |    |    |  (664 |   
 |    |    |  (399 |   
 |    |    |  (2,820 |   
 |    |    |  (2,408 |   
 |     |  
 |    |  $ |  43,527 |    |    |  $ |  39,426 |    |    |  $ |  110,581 |    |    |  $ |  109,222 |    |      
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