Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data	Jul. 03, 2011	Dec. 31, 2010
Current Assets
Allowance for doubtful debts	$ 1,253	$ 1,269
Accumulated depreciation on property, plant and equipment	$ 242,471	$ 244,662
Shareholders' Equity
Preferred stock, without par value	$ 0	$ 0
Preferred stock, shares authorized	25,000,000	25,000,000
Preferred stock, shares issued	0	0
Common stock, no par value	$ 0	$ 0
Common stock, shares authorized	75,000,000	75,000,000
Common stock, shares issued	54,788,197	54,517,560
Treasury stock, shares	20,356,259	20,320,759