Benefit Plans - Benefit Plan Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Retirement Benefits [Abstract]
Service cost	$ 509	$ 533	$ 1,523	$ 1,599
Interest cost	777	501	2,374	1,503
Expected return on plan assets	(773)	(540)	(2,384)	(1,620)
Amortization of prior service	60	74	184	222
Net periodic benefit cost	$ 573	$ 568	$ 1,697	$ 1,704