Noncontrolling interests (Details) (USD $)	3 Months Ended			3 Months Ended				3 Months Ended
	Apr. 01, 2012	Apr. 03, 2011	Dec. 31, 2011 Common Stock [Member]	Apr. 01, 2012 Additional Paid-in Capital [Member]	Apr. 01, 2012 Retained Earnings [Member]	Apr. 01, 2012 Accumulated Other Comprehensive Income (Loss) [Member]	Dec. 31, 2011 Treasury Stock [Member]	Apr. 01, 2012 Noncontrolling Interest [Member]
Balance as of December 31, 2011	$ 768,020,000		$ 2,900,000	$ 335,100,000	$ 963,100,000	$ (45,300,000)	$ (514,200,000)	$ 26,400,000
Net income	18,608,000	16,690,000			18,000,000			600,000
Other comprehensive income	10,300,000					10,000,000		300,000
Dividends declared	(800,000)				(800,000)
Dividends to non-controlling interest	(200,000)							(200,000)
Employee benefit transactions	2,000,000			2,000,000
Income tax benefit arising from employee stock option	200,000			200,000
Stock based compensation	(300,000)			(300,000)
Balance as of April 1, 2012	$ 797,830,000		$ 2,900,000	$ 337,000,000	$ 980,300,000	$ (35,300,000)	$ (514,200,000)	$ 27,100,000