Pension Plan Pension plan net periodic benefit costs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 28, 2014	Mar. 29, 2013
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure
Service cost for benefits earned during the year	$ 2,940	$ 3,587
Interest cost on projected benefit obligation	7,209	6,399
Expected return on plan assets	(10,262)	(10,337)
Amortization of prior service cost (credit)	25	25
Recognized net loss	1,019	2,277
Net pension benefit cost	931	1,951
Supplemental Employee Retirement Plans [Member]
Defined Benefit Plan Disclosure
Service cost for benefits earned during the year	64	85
Interest cost on projected benefit obligation	85	72
Expected return on plan assets	0	0
Amortization of prior service cost (credit)	0	0
Recognized net loss	22	77
Net pension benefit cost	$ 171	$ 234