Retirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 28, 2013	Jun. 29, 2012	Jun. 28, 2013	Jun. 29, 2012
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,789	$ 1,724	$ 3,590	$ 3,014
Interest cost	3,429	3,567	6,998	6,798
Expected return on assets	(4,535)	(3,859)	(9,249)	(7,684)
Amortization and other	2,789	3,049	5,292	5,495
Net periodic benefit cost	3,472	4,481	6,631	7,623
Postretirement Medical [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	155	125	310	275
Interest cost	247	237	493	500
Amortization	(50)	(38)	(102)	(75)
Net periodic benefit cost	$ 352	$ 324	$ 701	$ 700