Debt - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Dec. 31, 2017
Line of Credit Facility [Line Items]
Line of Credit Facility, Initiation Date				Oct. 30, 2015
Long-term debt	$ 6,310,000		$ 6,310,000	$ 4,435,000
Maximum amount outstanding	10,400,000	$ 5,700,000
Average amount outstanding	$ 3,500,000	$ 2,100,000
Weighted-average interest rate	3.30%	2.90%	3.30%
Debt covenants, Maximum leverage ratio			1.10%
Debt covenants, Minimum tangible net worth			$ 5,000,000
Debt covenants, Maximum capital expenditures			$ 5,000,000
Fixed charge coverage ratio	5.625		5.625
Total available borrowings	$ 31,100,000		$ 31,100,000
Debt covenants, EBITDA			7,700,000
Capital expenditures			$ 1,300,000
Federal Funds Effective Swap Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.50%
Minimum [Member] | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate				1.50%
Minimum [Member] | Adjusted London Interbank Offered Rate L I B O R
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.50%
Maximum [Member] | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate				2.00%
Maximum [Member] | Adjusted London Interbank Offered Rate L I B O R
Line of Credit Facility [Line Items]
Basis spread on variable rate				1.00%
Credit and Security Agreement [Member]
Line of Credit Facility [Line Items]
Revolving credit facility, term				3 years
Line of Credit Facility, Maximum Borrowing Capacity				$ 45,000,000
Line of credit facility, expiration date				2020-12
Letters of Credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 10,000,000
Swing Line Loans [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 10,000,000