Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 01, 2016	Oct. 03, 2015	Oct. 01, 2016	Oct. 03, 2015	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)	$ 1,234	$ (6,932)	$ 9,863	$ (6,714)
Effective income tax expense (benefit) rate	19.80%	(42.10%)	30.50%	(40.90%)
Unrecognized tax benefits	$ 2,900		$ 2,900		$ 3,000
Expected reduction in unrecognized tax benefits	$ 2,000		2,000
Pittsburgh and Miltec Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on Divestitures			$ 18,800