Retirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Retirement Benefits [Abstract]
Service cost	$ 709	$ 357	$ 1,413	$ 708
Interest cost	448	496	894	990
Recognized net actuarial loss	354	214	707	428
Net periodic benefit cost	$ 1,511	$ 1,067	$ 3,014	$ 2,126
Defined Benefit Plan, Type [Extensible Enumeration]			us-gaap:PensionPlansDefinedBenefitMember