CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Apr. 02, 2011
Trade accounts receivable, allowances (in dollars)	$ 1,618	$ 1,731	$ 1,824
Treasury stock, shares	73	71	71
Common stock
Common stock, par value (in dollars per share)	$ 0.6944	$ 0.6944	$ 0.6944
Common stock, shares authorized	120,000	120,000	120,000
Common stock, shares issued	37,390	36,479	37,087
Class B common stock
Common stock, par value (in dollars per share)	$ 0.6944	$ 0.6944	$ 0.6944
Common stock, shares authorized	40,000	40,000	40,000
Common stock, shares issued	21,652	21,025	21,051