Retirement Plans (Components of Net Periodic Benefits Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,800	$ 3,450
Interest cost	3,417	3,460
Expected return on plan assets	(11,475)	(12,058)
Amortization of net (gain) or loss and prior service costs	1,348	2,100
Net reduction of periodic benefit cost	(3,910)	(3,048)
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	25	27
Interest cost	77	99
Amortization of net (gain) or loss and prior service costs	(139)	(146)
Net reduction of periodic benefit cost	$ (37)	$ (20)