Pension Plan Pension plan net periodic benefit costs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 27, 2013	Sep. 28, 2012	Sep. 27, 2013	Sep. 28, 2012
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure
Service cost for benefits earned during the year	$ 3,587	$ 3,519	$ 10,761	$ 10,557
Interest cost on projected benefit obligation	6,399	6,578	19,197	19,734
Expected return on plan assets	(10,337)	(9,470)	(31,011)	(28,409)
Amortization of prior service cost (credit)	25	24	75	74
Recognized net loss	2,387	1,962	6,968	5,883
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments			0	0
Net pension benefit cost	2,061	2,613	5,990	7,839
Supplemental Employee Retirement Plans [Member]
Defined Benefit Plan Disclosure
Service cost for benefits earned during the year	85	96	255	287
Interest cost on projected benefit obligation	78	105	233	315
Expected return on plan assets	0	0	0	0
Amortization of prior service cost (credit)	0	0	0	0
Recognized net loss	65	39	195	118
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments			277	0
Net pension benefit cost	$ 228	$ 240	$ 960	$ 720