Adoption of Accounting Standards Codification 606 - Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net Income	$ 2,600	$ 2,115
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Depreciation and amortization	5,981	5,782
Property and equipment impairment due to restructuring	1,077	0
Stock-based compensation expense	1,090	1,822
Deferred income taxes	(206)	532
(Recovery of) provision for doubtful accounts	(143)	26
Other	8,810	(1,860)
Changes in Assets and Liabilities:
Accounts receivable	9,292	4,590
Contract assets	(78,163)	0
Inventories	36,229	(7,305)
Production cost of contracts	(55)	45
Other assets	412	610
Accounts payable	12,213	6,465
Contract liabilities	15,723	0
Accrued and other liabilities	(4,524)	415
Net Cash Provided by Operating Activities	10,336	13,237
Cash Flows from Investing Activities
Purchases of property and equipment	(3,341)	(6,797)
Proceeds from sale of assets	41	3
Net Cash Used in Investing Activities	(3,300)	(6,794)
Cash Flows from Financing Activities
Borrowings from senior secured revolving credit facility	76,700	55,600
Repayments of senior secured revolving credit facility	(83,300)	(55,600)
Net cash paid upon issuance of common stock under stock plans	(789)	(1,758)
Net Cash Used in Financing Activities	(7,389)	(6,761)
Net Decrease in Cash and Cash Equivalents	(353)	(318)
Cash and Cash Equivalents at Beginning of Period	2,150	7,432
Cash and Cash Equivalents at End of Period	1,797	$ 7,114
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net Income	(1,718)
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Depreciation and amortization	0
Property and equipment impairment due to restructuring	0
Stock-based compensation expense	0
Deferred income taxes	(3,116)
(Recovery of) provision for doubtful accounts	0
Other	(8,975)
Changes in Assets and Liabilities:
Accounts receivable	0
Contract assets	78,163
Inventories	(51,918)
Production cost of contracts	0
Other assets	(1,066)
Accounts payable	0
Contract liabilities	(15,723)
Accrued and other liabilities	4,353
Net Cash Provided by Operating Activities	0
Cash Flows from Investing Activities
Purchases of property and equipment	0
Proceeds from sale of assets	0
Net Cash Used in Investing Activities	0
Cash Flows from Financing Activities
Borrowings from senior secured revolving credit facility	0
Repayments of senior secured revolving credit facility	0
Net cash paid upon issuance of common stock under stock plans	0
Net Cash Used in Financing Activities	0
Net Decrease in Cash and Cash Equivalents	0
Cash and Cash Equivalents at Beginning of Period	0
Cash and Cash Equivalents at End of Period	0
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net Income	882
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Depreciation and amortization	5,981
Property and equipment impairment due to restructuring	1,077
Stock-based compensation expense	1,090
Deferred income taxes	(3,322)
(Recovery of) provision for doubtful accounts	(143)
Other	(165)
Changes in Assets and Liabilities:
Accounts receivable	9,292
Contract assets	0
Inventories	(15,689)
Production cost of contracts	(55)
Other assets	(654)
Accounts payable	12,213
Contract liabilities	0
Accrued and other liabilities	(171)
Net Cash Provided by Operating Activities	10,336
Cash Flows from Investing Activities
Purchases of property and equipment	(3,341)
Proceeds from sale of assets	41
Net Cash Used in Investing Activities	(3,300)
Cash Flows from Financing Activities
Borrowings from senior secured revolving credit facility	76,700
Repayments of senior secured revolving credit facility	(83,300)
Net cash paid upon issuance of common stock under stock plans	(789)
Net Cash Used in Financing Activities	(7,389)
Net Decrease in Cash and Cash Equivalents	(353)
Cash and Cash Equivalents at Beginning of Period	2,150
Cash and Cash Equivalents at End of Period	$ 1,797