Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016
Cash Flows from Operating Activities
Net Income	$ 10,593	$ 22,425
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Depreciation and amortization	17,149	17,420
Gain on divestitures	0	(18,815)
Stock-based compensation expense	4,264	2,579
Deferred income taxes	(164)	(1,602)
Provision for (recovery of) doubtful accounts	125	(26)
Other	(2,217)	(4,923)
Changes in Assets and Liabilities:
Accounts receivable	(1,427)	5,777
Inventories	(15,529)	(15,055)
Production cost of contracts	(599)	(1,437)
Other assets	458	7,095
Accounts payable	13,801	19,586
Accrued and other liabilities	903	(5,453)
Net Cash Provided by Operating Activities	27,357	27,571
Cash Flows from Investing Activities
Purchases of property and equipment	(24,599)	(12,712)
Proceeds from sale of assets	3	0
Insurance recoveries related to property and equipment	288	0
Proceeds from divestitures	0	55,272
Payments for purchase of Lightning Diversion Systems, LLC, net of cash acquired	(59,178)	0
Net Cash (Used in) Provided by Investing Activities	(83,486)	42,560
Cash Flows from Financing Activities
Borrowings from senior secured revolving credit facility	320,500	29,700
Repayments of senior secured revolving credit facility	(255,800)	(29,700)
Repayments of senior unsecured notes and term loans	(10,000)	(65,000)
Repayments of other debt	(3)	(22)
Net cash paid upon issuance of common stock under stock plans	(2,311)	(1,097)
Net Cash Provided by (Used in) Financing Activities	52,386	(66,119)
Net (Decrease) Increase in Cash and Cash Equivalents	(3,743)	4,012
Cash and Cash Equivalents at Beginning of Period	7,432	5,454
Cash and Cash Equivalents at End of Period	$ 3,689	$ 9,466