Retirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Retirement Benefits [Abstract]
Service cost	$ 693	$ 362	$ 2,106	$ 1,073
Interest cost	443	498	1,337	1,488
Recognized net actuarial loss	353	214	1,060	642
Net periodic benefit cost	$ 1,489	$ 1,074	$ 4,503	$ 3,203
Defined Benefit Plan, Type [Extensible Enumeration]			Pension Plan [Member]