Pension and Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2015	Sep. 28, 2014	Sep. 27, 2015	Sep. 28, 2014
Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1,006	$ 921	$ 3,038	$ 2,861
Interest cost	4,603	4,953	13,827	15,064
Expected return on assets	(5,476)	(5,469)	(16,452)	(16,587)
Net amortization and deferrals	2,202	1,210	6,610	3,713
Curtailment/settlement losses	643	0	781	0
Net periodic benefit cost	2,978	1,615	7,804	5,051
Contributions to defined benefit pension plans			10,760
Expected contributions during the remainder of fiscal year			3,240
Postretirement [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	150	137	450	412
Interest cost	285	332	855	997
Expected return on assets	0	0	0	0
Net amortization and deferrals	(114)	(114)	(341)	(341)
Curtailment/settlement losses	(3,842)	0	(3,842)	0
Net periodic benefit cost	$ (3,521)	$ 355	$ (2,878)	$ 1,068