Debt - Details of Debt (Detail) - USD ($) $ in Thousands		Sep. 29, 2018	Dec. 31, 2017
Outstanding Debt:
Unamortized debt issuance costs		$ (1,124)	$ (1,261)
Outstanding Debt		329,261	247,978
Less current portion of long-term debt		84,956	40,870
Total long-term debt, net of current portion		$ 244,305	207,108
Amended Credit Facility [Member]
Outstanding Debt:
Credit facility, Interest Rates	[1]	10.13%
Amended Credit Facility [Member] | Term Loan [Member]
Outstanding Debt:
Outstanding Debt	[1]	$ 30,000
Amended Credit Facility [Member] | Revolver [Member]
Outstanding Debt:
Outstanding Debt	[1]	$ 99,110	70,225
Amended Credit Facility [Member] | Revolver [Member] | Minimum [Member]
Outstanding Debt:
Credit facility, Interest Rates	[1]	3.88%
Amended Credit Facility [Member] | Revolver [Member] | Maximum [Member]
Outstanding Debt:
Credit facility, Interest Rates	[1]	6.00%
Westport Facility [Member]
Outstanding Debt:
Credit facility, Interest Rates	[2]	5.13%
Westport Facility [Member] | Term Loan [Member]
Outstanding Debt:
Outstanding Debt	[2]	$ 15,500	22,500
Equipment Financing [Member]
Outstanding Debt:
Outstanding Debt	[3]	$ 133,187	112,205
Equipment Financing [Member] | Minimum [Member]
Outstanding Debt:
Credit facility, Interest Rates	[3]	3.18%
Equipment Financing [Member] | Maximum [Member]
Outstanding Debt:
Credit facility, Interest Rates	[3]	4.99%
Real Estate Financing [Member]
Outstanding Debt:
Outstanding Debt	[4]	$ 47,337	$ 44,309
Credit facility, Interest Rates	[4]	4.51%
Margin Facility [Member]
Outstanding Debt:
Outstanding Debt	[5]	$ 5,251
Credit facility, Interest Rates	[5]	3.36%

[1] The Amended Credit Facility provides for maximum borrowings of $180 million in the form of a $30 million term loan and a $150 million revolver. Borrowings under the revolver may be made until the maturity date, December 23, 2020. Borrowings under the term loan were advanced on August 10, 2018 and mature on August 10, 2019. The term loan will be repaid in equal monthly installments of $357,000 commencing on October 1, 2018, with the remaining principal balance and all unpaid interest due at maturity. Borrowings under the Amended Credit Facility bear interest at LIBOR or a base rate, plus an applicable margin. The applicable margin for advances under the revolver fluctuates based on excess availability. The applicable margin for the term loan is 5.50% plus 2.5% of paid-in-kind interest (“PIK Interest”). PIK Interest compounds monthly and is due and payable up to the maturity of the term loan. The revolver is secured by cash, deposits, accounts receivable and selected other assets of the applicable borrowers. The term loan is secured by a first priority perfected security interest and pledge of the Company’s applicable operating entities. The facility also includes customary affirmative and negative covenants and events of default, as well as financial covenants requiring a minimum fixed charge coverage ratio to be maintained after a triggering event. At September 29, 2018, we were in compliance with all covenants under the facility, and $38.3 million was available for borrowing.

[2] The Westport Facility provides our subsidiary, Westport Axle Corporation, with maximum borrowings of $60 million in the form of a $40 million term loan and a $20 million revolver. Borrowings under the Westport Facility, which matures on December 23, 2020, accrue interest either at a variable interest rate based on LIBOR or at a base-rate, and are secured by all of Westport’s assets. The Company becomes a guarantor upon the occurrence of certain events specified in the Westport Facility. Borrowings are repaid in part quarterly with the balance due at maturity. Interest on base rate advances is payable quarterly, and interest on each LIBOR-based advance is payable on the last day of the applicable interest period. The Westport Facility includes customary affirmative and negative covenants and events of default. At September 29, 2018, we were in compliance with all covenants, and $16.7 million was available for borrowing.

[3] The Equipment Financing consists of a series of promissory notes issued by a wholly-owned subsidiary in order to finance transportation equipment. The equipment notes, which are secured by liens on selected titled vehicles, include certain affirmative and negative covenants, are generally payable in 60 monthly installments and bear interest at fixed rates ranging from 3.18% to 4.99%. At September 29, 2018, we were in compliance with all covenants.

[4] The Real Estate Financing consists of a series of promissory notes issued by a wholly-owned subsidiary in order to finance certain real property. The promissory notes, which are secured by first mortgages and assignment of leases on specific parcels of real estate and improvements, include certain affirmative and negative covenants and are generally payable in 120 monthly installments. Each of the notes bears interest at LIBOR plus 2.25%. At September 29, 2018, we were in compliance with all covenants.

[5] The Margin Facility is a short-term line of credit secured by our portfolio of marketable securities. It bears interest at LIBOR plus 1.10%. The amount available under the line of credit is based on a percentage of the market value of the underlying securities. At September 29, 2018, the maximum available borrowing under the line of credit was $41,000.