Pension Plan Pension plan net periodic benefit costs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2012	Sep. 30, 2011	Sep. 28, 2012	Sep. 30, 2011
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure
Service cost for benefits earned during the year	$ 3,519	$ 3,021	$ 10,557	$ 9,061
Interest cost on projected benefit obligation	6,578	7,082	19,734	21,244
Expected return on plan assets	(9,470)	(8,926)	(28,409)	(26,482)
Amortization of prior service cost (credit)	24	25	74	74
Recognized net loss	1,962	1,038	5,883	2,823
Additional amount recognized due to curtailment/settlement			0	0
Net pension benefit cost	2,613	2,240	7,839	6,720
Supplemental Employee Retirement Plans [Member]
Defined Benefit Plan Disclosure
Service cost for benefits earned during the year	96	90	287	270
Interest cost on projected benefit obligation	105	129	315	387
Expected return on plan assets	0	0	0	0
Amortization of prior service cost (credit)	0	0	0	0
Recognized net loss	39	38	118	114
Additional amount recognized due to curtailment/settlement			0	560
Net pension benefit cost	$ 240	$ 257	$ 720	$ 1,331