Retirement Plans (Schedule of Net Periodic (Benefit) Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2015	Jun. 28, 2014	Jun. 27, 2015	Jun. 28, 2014
Net Periodic Benefit Cost [Abstract]
Service cost	$ 0	$ 0	$ 1	$ 1
Interest cost	3,524	3,707	7,048	7,413
Expected return on plan assets	(5,226)	(5,206)	(10,452)	(10,412)
Net amortization and deferral	0	0	0	0
Net amortization and deferral	2,156	794	4,312	1,587
Net periodic expense (benefit)	$ 454	$ (705)	$ 909	$ (1,411)