Annual report pursuant to Section 13 and 15(d)

Property, Plant and Equipment (Details)

v3.6.0.2
Property, Plant and Equipment (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 457,510 $ 437,188
Less accumulated depreciation 251,288 236,804
Net book value 206,222 200,384
Land    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 10,463 10,463
Buildings    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 65,894 64,154
Property, plant and equipment, estimated useful life 25 years  
Machinery and equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 238,029 223,521
Furniture and fixtures    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 5,570 5,354
Transportation equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 3,814 3,481
Improvements    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 128,437 127,727
Property, plant and equipment, estimated useful life 15 years  
Construction in progress    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 5,303 $ 2,488
Minimum    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, estimated useful life 3 years  
Minimum | Machinery and equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, estimated useful life 3 years  
Minimum | Furniture and fixtures    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, estimated useful life 3 years  
Minimum | Transportation equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, estimated useful life 3 years  
Maximum    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, estimated useful life 25 years  
Maximum | Machinery and equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, estimated useful life 25 years  
Maximum | Furniture and fixtures    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, estimated useful life 5 years  
Maximum | Transportation equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, estimated useful life 5 years