Pension and Other Postretirement Benefits - Pension Benefits - Net Periodic Pension Cost (Details) - Pension Plan - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Apr. 01, 2018
Pension Benefits
Service cost	$ 1,278	$ 2,647
Interest cost	16,797	14,999
Expected return on plan assets	(20,258)	(20,555)
Amortization of actuarial loss	5,729	8,056
Amortization of prior service credit	(486)	(486)
Net periodic postretirement benefit income	3,060	4,661
Qualified Plans
Pension Benefits
Service cost	1,278	2,647
Interest cost	14,709	13,151
Expected return on plan assets	(20,258)	(20,555)
Amortization of actuarial loss	4,635	6,762
Amortization of prior service credit	(486)	(486)
Net periodic postretirement benefit income	(122)	1,519
Pension contributions	2,000	2,100
Expected contributions in 2018	9,000
Non- Qualified Plans
Pension Benefits
Service cost	0	0
Interest cost	2,088	1,848
Expected return on plan assets	0	0
Amortization of actuarial loss	1,094	1,294
Amortization of prior service credit	0	0
Net periodic postretirement benefit income	$ 3,182	$ 3,142