Debt - Details of Debt (Parenthetical) (Detail)	9 Months Ended
	Sep. 29, 2018 USD ($) Installment
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR rate plus 2.25%
Amended Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, borrowing capacity	$ 180,000,000
Credit facility available for borrowings	38,300,000
Amended Credit Facility [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Term loan, face amount	$ 30,000,000
Term loan, maturity date	Aug. 10, 2019
Term loan, periodic payment	$ 357,000
Term loan, frequency of payments	monthly
Term loan, payment commencement date	Oct. 01, 2018
Term loan, applicable margin rate	5.50%
Term loan, applicable margin paid in kind interest	2.50%
Amended Credit Facility [Member] | Revolver [Member]
Debt Instrument [Line Items]
Credit facility, borrowing capacity	$ 150,000,000
Credit facility, expiration date	Dec. 23, 2020
Westport Facility [Member]
Debt Instrument [Line Items]
Credit facility, borrowing capacity	$ 60,000,000
Credit facility, expiration date	Dec. 23, 2020
Credit facility available for borrowings	$ 16,700,000
Westport Facility [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Term loan, face amount	40,000,000
Westport Facility [Member] | Revolver [Member]
Debt Instrument [Line Items]
Credit facility, borrowing capacity	$ 20,000,000
Equipment Financing [Member]
Debt Instrument [Line Items]
Number of installments | Installment	60
Frequency of installments	monthly
Equipment Financing [Member] | Minimum [Member]
Debt Instrument [Line Items]
Credit facility, Interest Rates	3.18%	[1]
Equipment Financing [Member] | Maximum [Member]
Debt Instrument [Line Items]
Credit facility, Interest Rates	4.99%	[1]
Equipment Financing [Member] | Secured Debt
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR plus 2.25%
Debt instrument payable number of monthly installments | Installment	120
Equipment Financing [Member] | Secured Debt | LIBOR [Member]
Debt Instrument [Line Items]
Term loan, applicable margin rate	2.25%
Margin Facility [Member]
Debt Instrument [Line Items]
Credit facility available for borrowings	$ 41,000
Description of variable rate basis	LIBOR plus 1.10%
Margin Facility [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Term loan, applicable margin rate	1.10%

[1] 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.