Adoption of Accounting Standards Codification 606 - Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net Income	$ 673	$ 4,171	$ 1,591	$ 2,600	$ 9,484	$ 4,655	$ 3,823	$ 2,115	$ 9,035	$ 20,077	$ 25,261
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Depreciation and amortization									25,296	22,845	22,860
Property and equipment impairment due to restructuring									6,207	3,607	0
Stock-based compensation expense									5,040	4,675	3,007
Deferred income taxes									2,042	(15,411)	3,519
Provision for doubtful accounts									267	373	112
Noncash loss on extinguishment of debt									926	0	0
Other									11,659	(1,182)	(7,204)
Changes in Assets and Liabilities:
Accounts receivable									7,495	2,720	3,220
Contract assets									(86,665)	0	0
Inventories									23,243	(533)	(5,182)
Production cost of contracts									(1,569)	(267)	(1,536)
Other assets									1,881	40	2,974
Accounts payable									18,496	(4,015)	15,055
Contract liabilities									17,145	0	0
Accrued and other liabilities									5,739	2,505	(966)
Net Cash Provided by Operating Activities									46,237	35,434	43,268
Cash Flows from Investing Activities
Purchases of property and equipment									(17,617)	(27,610)	(17,001)
Proceeds from sale of assets									396	913	16
Payments for acquisition of Certified Thermoplastics Co., LLC, net of cash acquired									(30,712)	0	0
Net Cash (Used in) Provided by Investing Activities									(47,933)	(86,207)	34,908
Cash Flows from Financing Activities
Borrowings from senior secured revolving credit facility									296,400	395,900	71,800
Repayment of senior secured revolving credit facility									(354,500)	(337,800)	(71,800)
Borrowings from term loan									240,000	0	0
Repayments of term loan									(167,000)	(10,000)	(75,000)
Debt issuance costs									(3,541)	0	0
Net cash paid from issuance of common stock under stock plans									(1,550)	(2,606)	(1,423)
Net Cash Provided by (Used in) Financing Activities									9,809	45,491	(76,198)
Net (Decrease) Increase in Cash and Cash Equivalents									8,113	(5,282)	1,978
Cash and Cash Equivalents at Beginning of Year				2,150				$ 7,432	2,150	7,432	5,454
Cash and Cash Equivalents at End of Year	10,263				2,150				10,263	2,150	$ 7,432
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									(4,660)
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									(2,578)
Provision for doubtful accounts									0
Noncash loss on extinguishment of debt									0
Other									(8,364)
Changes in Assets and Liabilities:
Accounts receivable									0
Contract assets									86,665
Inventories									(57,527)
Production cost of contracts									0
Other assets									(1,084)
Accounts payable									0
Contract liabilities									(17,145)
Accrued and other liabilities									4,693
Net Cash Provided by Operating Activities									0
Cash Flows from Investing Activities
Purchases of property and equipment									0
Proceeds from sale of assets									0
Payments for acquisition of Certified Thermoplastics Co., LLC, net of cash acquired									0
Net Cash (Used in) Provided by Investing Activities									0
Cash Flows from Financing Activities
Borrowings from senior secured revolving credit facility									0
Repayment of senior secured revolving credit facility									0
Borrowings from term loan									0
Repayments of term loan									0
Debt issuance costs									0
Net cash paid from issuance of common stock under stock plans									0
Net Cash Provided by (Used in) Financing Activities									0
Net (Decrease) Increase in Cash and Cash Equivalents									0
Cash and Cash Equivalents at Beginning of Year				0					0
Cash and Cash Equivalents at End of Year	0				0				0	0
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net Income									4,375
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Depreciation and amortization									25,296
Property and equipment impairment due to restructuring									6,207
Stock-based compensation expense									5,040
Deferred income taxes									(536)
Provision for doubtful accounts									267
Noncash loss on extinguishment of debt									926
Other									3,295
Changes in Assets and Liabilities:
Accounts receivable									7,495
Contract assets									0
Inventories									(34,284)
Production cost of contracts									(1,569)
Other assets									797
Accounts payable									18,496
Contract liabilities									0
Accrued and other liabilities									10,432
Net Cash Provided by Operating Activities									46,237
Cash Flows from Investing Activities
Purchases of property and equipment									(17,617)
Proceeds from sale of assets									396
Payments for acquisition of Certified Thermoplastics Co., LLC, net of cash acquired									(30,712)
Net Cash (Used in) Provided by Investing Activities									(47,933)
Cash Flows from Financing Activities
Borrowings from senior secured revolving credit facility									296,400
Repayment of senior secured revolving credit facility									(354,500)
Borrowings from term loan									240,000
Repayments of term loan									(167,000)
Debt issuance costs									(3,541)
Net cash paid from issuance of common stock under stock plans									(1,550)
Net Cash Provided by (Used in) Financing Activities									9,809
Net (Decrease) Increase in Cash and Cash Equivalents									8,113
Cash and Cash Equivalents at Beginning of Year				$ 2,150					2,150
Cash and Cash Equivalents at End of Year	$ 10,263				$ 2,150				$ 10,263	$ 2,150