Pension and Postretirement Benefits - Components of Net Periodic Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 325	$ 678	$ 2,170	$ 2,030
Interest cost	821	3,997	7,939	11,993
Expected return on assets	(476)	(5,190)	(7,642)	(15,569)
Settlement	0	0	110,777	0
Net amortization and deferrals	598	2,971	7,906	8,913
Net periodic benefit cost	1,268	2,456	121,150	7,367
Postretirement
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	311	189	667	566
Interest cost	316	292	948	877
Expected return on assets	0	0	0	0
Settlement	0	0	0	0
Net amortization and deferrals	5	42	15	127
Net periodic benefit cost	$ 632	$ 523	$ 1,630	$ 1,570