Business Segments - Sales to Customers Contributing Ten Percent or More of Consolidated Sales (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Ford [Member]
Revenue, Major Customer [Line Items]
Major customers	28.00%	27.00%	26.00%
General Motors [Member]
Revenue, Major Customer [Line Items]
Major customers	19.00%	17.00%	16.00%
Fiat Chrysler Automobiles [Member]
Revenue, Major Customer [Line Items]
Major customers	11.00%	12.00%	12.00%