Significant Accounting Policies Update (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2018	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ (578,293)	$ (596,270)		$ (596,270)		$ (587,877)
Net sales		468,129	$ 449,006	931,456	$ 884,947
Gross profit		135,643	134,493	269,750	258,839
Contract liabilities, noncurrent portion	689	76,330		76,330		$ 0
Cost to Fulfill Contract
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized contract cost		9,500		9,500
Costs to Obtain Contract
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized contract cost		6,800		6,800
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	9,584	127		127
Net sales		(18,473)		(61,974)
Gross profit		(5,103)		(15,346)
Contract liabilities, noncurrent portion	689	(76,330)		(76,330)
Aerospace
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales		178,606	170,300	358,001	334,623
Increase to operating income from the quarterly impact of revisions in long term contracts			$ 1,100		$ 2,100
Aerospace | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	32,500
Write-off of inventory	32,500
Net sales	62,300
Gross profit	$ 20,200
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-06-29
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected revenue from backlog		585,600		585,600
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected revenue from backlog		969,000		969,000
Performance obligations satisfied in previous periods [Member] | Aerospace
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales		$ 1,400		$ 3,000