Retirement Plans (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) Facility	Jun. 30, 2017 USD ($)
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	$ 465	$ 734	$ 926
Interest cost	286	359	575	714
Expected return on plan assets	(241)	(259)	(486)	(514)
Amortization of actuarial gain	(27)	(21)	(54)	(42)
Settlement expense	0	3,797	0	3,797
Total defined benefit expense	$ 384	$ 4,341	$ 769	$ 4,881