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Segment and Geographic Area Information - Revenue Percent by Major Customers (Details) - Net Sales
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
General Motors      
Revenue, Major Customer [Line Items]      
Customer accounted for ten percent or more of net sales 14.00% 17.00% 15.00%
Ford      
Revenue, Major Customer [Line Items]      
Customer accounted for ten percent or more of net sales 13.00% 13.00% 14.00%