| Summary of property, plant and equipment | 
 
		
			
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						December 31, 
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						2015 
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						2014 
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						Land  
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						$ 
				 | 
				
1,500
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				 | 
				
					 
						$ 
				 | 
				
1,500
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						Land improvements  
				 | 
				
					 
						  
				 | 
				
3,010
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				 | 
				
2,292
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						Leasehold improvements 
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				 | 
				
859
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				 | 
				
499
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						Buildings  
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24,476
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21,918
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						Machinery and equipment  
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35,628
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31,780
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						Furniture and fixtures  
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				 | 
				
11,657
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				 | 
				
10,070
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						Mobile equipment and other  
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				 | 
				
2,255
				 | 
				
					 
						  
				 | 
				
1,999
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						Construction-in-process  
				 | 
				
					 
						  
				 | 
				
2,155
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				 | 
				
1,930
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						Total property, plant and equipment  
				 | 
				
					 
						  
				 | 
				
81,540
				 | 
				
					 
						  
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71,988
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						Less accumulated depreciation  
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				 | 
				
(38,904)
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(34,442)
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						Net property, plant and equipment  
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
42,636
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						$ 
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37,546
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