Fair Value Measurements (Details 3) (USD $) In Thousands, unless otherwise specified								3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Apr. 02, 2011	Mar. 31, 2012 Cost Basis	Apr. 02, 2011 Cost Basis	Mar. 31, 2012 Estimated Fair Value	Apr. 02, 2011 Estimated Fair Value	Mar. 31, 2012 Auction rate security	Apr. 02, 2011 Auction rate security	Dec. 31, 2010 Auction rate security
Level 3 reconciliation
Balance at the beginning of the period								$ 7,453	$ 6,775	$ 6,775
Unrealized Loss in other comprehensive earnings								(678)
Balance at the end of the period								6,775	6,775	6,775
Industrial revenue development bonds, carrying amount, approximates fair value	$ 7,500	$ 7,500	$ 7,500	$ 7,500	$ 7,500	$ 7,500	$ 7,500