Retirement Plans (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Facility	Sep. 30, 2017 USD ($)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Number of facilities associated with the defined benefit plan closed under the restructuring plan | Facility				2
Defined Benefit Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 366	$ 466		$ 1,100	$ 1,392
Interest cost	282	366		857	1,080
Expected return on plan assets	(236)	(264)		(722)	(778)
Amortization of actuarial gain	(27)	(19)		(81)	(61)
Settlement expense	0	0	$ 3,800	0	3,797
Total defined benefit expense	$ 385	$ 549		$ 1,154	$ 5,430