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Inventory (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Inventory [Line Items]      
Percentage of LIFO Inventory 90.00% 93.00%  
Excess of Replacement or Current Costs over Stated LIFO Value $ 147,091 $ 136,143  
Document Fiscal Year Focus 2016    
Inventory, LIFO Reserve, Effect on Income, Net $ 131    
Inventory Valuation Reserves 6,553 4,912  
Inventory Valuation Reserve      
Inventory [Line Items]      
Reserves for Obsolete Inventories, Period Increase (Decrease) $ 1,641 $ 495 $ 670