Long-Term Debt and Commitments (Details) (USD $)	6 Months Ended
	Jun. 30, 2013	Jul. 01, 2012	Dec. 31, 2012
Debt Instrument [Line Items]
Long-term debt, gross	$ 83,800,000		$ 85,500,000
Less: Current maturities	75,566,000		76,977,000
Long-term debt	8,200,000		8,478,000
Repayment of long-term debt	1,705,000	280,000
Short-term Borrowings [Abstract]
Uncommitted short-term bank credit lines, maximum borrowing capacity	190,400,000
Uncommitted short-term bank credit lines, amount outstanding	7,021,000		7,111,000
Series 2006 Senior Notes Due 2013 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	50,000,000		50,000,000
Interest rate on debt instrument (in hundredths)	5.53%
Maturity date	Oct. 05, 2013
Floating Rate Series 2006 A Senior Notes Due 2013 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	25,000,000		25,000,000
Maturity date	Oct. 05, 2013
Variable/Fixed Rate Industrial Development Revenue Bonds Series 1999 Due 2014 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	8,200,000		8,200,000
Maturity date	Nov. 01, 2014
Installment Obligations [Member]
Debt Instrument [Line Items]
Long-term debt, gross	0		1,400,000
Repayment of long-term debt	1,400,000
Other Borrowings [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 600,000		$ 900,000