Fair Value Measurements - Investments (Details) (USD $) In Thousands, unless otherwise specified										3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 27, 2014	Dec. 31, 2013	Sep. 28, 2013	Sep. 27, 2014 Cost Basis Level 2	Dec. 31, 2013 Cost Basis Level 2	Sep. 28, 2013 Cost Basis Level 2	Sep. 27, 2014 Estimated Fair Value Level 2	Dec. 31, 2013 Estimated Fair Value Level 2	Sep. 28, 2013 Estimated Fair Value Level 2	Dec. 31, 2013 Jefferson County Alabama Sewer Revenue Refunding Warrants Auction rate security	Sep. 28, 2013 Jefferson County Alabama Sewer Revenue Refunding Warrants Auction rate security Level 3	Dec. 31, 2008 Jefferson County Alabama Sewer Revenue Refunding Warrants Auction rate security Level 3	Dec. 31, 2008 Jefferson County Alabama Sewer Revenue Refunding Warrants AAA rating Auction rate security Level 3
Fair value on a recurring basis
Sale value of investment										$ 10,840
Purchase cost of investment													13,550
Other-than-temporary pre-tax impairment on investment												5,140
Carrying value of investment											10,162		8,410
Unrealized loss in other comprehensive earnings											677
Industrial revenue development bonds, carrying amount, approximates fair value	$ 7,500	$ 7,500	$ 7,500	$ 7,500	$ 7,500	$ 7,500	$ 7,500	$ 7,500	$ 7,500