Major Customers and Concentrations of Credit Risk - Sales to Major Customers (Detail) - Customer Concentration Risk - Sales Revenue, Net	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Boeing
Revenue, Major Customer [Line Items]
Concentration percentage	16.40%	17.30%	16.00%
Lockheed Martin
Revenue, Major Customer [Line Items]
Concentration percentage	5.50%	5.60%	1.20%
Raytheon
Revenue, Major Customer [Line Items]
Concentration percentage	13.50%	8.40%	8.70%
Spirit
Revenue, Major Customer [Line Items]
Concentration percentage	8.20%	8.20%	7.40%
United Technologies
Revenue, Major Customer [Line Items]
Concentration percentage	4.70%	5.30%	6.10%
Top Ten Customers
Revenue, Major Customer [Line Items]
Concentration percentage	62.50%	58.60%	55.70%