Long-Term Debt (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Sep. 01, 2016
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 18,200,000
Interest Expense, Debt	167,000	$ 273,000
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
Line of Credit Facility, Fair Value of Amount Outstanding	$ 17,900,000
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