Goodwill and Other Intangible Assets - Future Amortization Expense of Other Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2018	$ 10,157
2019	10,010
2020	9,838
2021	9,668
2022	9,608
Thereafter	65,412
Net Carrying Amount	114,693	$ 101,573
Structural Systems
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2018	737
2019	591
2020	490
2021	381
2022	320
Thereafter	317
Net Carrying Amount	2,836	3,745
Electronic Systems
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2018	9,420
2019	9,419
2020	9,348
2021	9,287
2022	9,288
Thereafter	65,095
Net Carrying Amount	$ 111,857	$ 97,828