Employee Benefits (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 27, 2014	Sep. 28, 2013	Jun. 29, 2013	Sep. 27, 2014	Sep. 28, 2013
Components of net periodic benefit cost:
Service cost	$ 1,924,000	$ 2,342,000		$ 5,784,000	$ 7,026,000
Interest cost	2,404,000	2,028,000		7,225,000	6,131,000
Expected return on plan assets	(2,173,000)	(1,615,000)		(6,537,000)	(4,841,000)
Amortization and other	524,000	1,565,000		1,575,000	4,744,000
Agreement termination gain			(3,204,000)		(3,204,000)
Net periodic benefit cost	2,679,000	4,320,000		8,047,000	9,856,000
Agreement termination gain, net of tax			1,954,000
Agreement termination gain unrecognized in other comprehensive income, before tax			2,148,000
Agreement termination gain unrecognized in other comprehensive income, net of tax			1,310,000		1,310,000
Defined benefit pension plan
Target allocation and pension plan asset allocation
Number of defined benefit plans	2			2
Contributions expected to be made to defined benefit pension plans				$ 0