Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Sep. 11, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2017
Goodwill And Intangible Assets [Line Items]
Goodwill		$ 117,435	$ 82,554
Purchase price, net of cash acquired		59,798	0	$ 0
Amortization expense of intangible asset		$ 9,300	9,000	$ 10,000
Minimum
Goodwill And Intangible Assets [Line Items]
Acquired intangible assets amortization period		14 years
Maximum
Goodwill And Intangible Assets [Line Items]
Acquired intangible assets amortization period		18 years
Electronic Systems
Goodwill And Intangible Assets [Line Items]
Goodwill		$ 117,435	$ 82,554
Goodwill fair value in excess of carrying value			32.00%
Lightning Diversion Systems, Inc.
Goodwill And Intangible Assets [Line Items]
Goodwill	$ 34,881
Equity interest acquired	100.00%				100.00%
Purchase price, net of cash acquired	$ 60,000
Gross purchase price	$ 62,021