Long-Term Debt (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017	Sep. 01, 2016
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 14,400,000		$ 14,400,000
Interest Expense, Debt	$ 73,000	$ 260,000	$ 240,000	$ 533,000
Revolving Credit Facility [Member] | Wells Fargo Bank, N.A. [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 100,000,000
Debt Instrument, Maturity Date			Sep. 01, 2019
Debt Instrument, Covenant, Minimum EBITDA			$ 75,000,000
Debt Instrument, Covenant Description			The only financial covenant in the credit facility requires the Company's trailing twelve month EBITDA to be at least $75.0 million
Revolving Credit Facility [Member] | Wells Fargo Bank, N.A. [Member] | London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate			0.65%
Line of Credit [Member] | Wells Fargo Bank, N.A. [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 50,000,000