Retirement Plans (Components of Net Periodic Benefits Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,979	$ 2,855	$ 5,938	$ 8,584
Interest cost	6,052	3,756	17,803	10,881
Expected return on plan assets	(11,177)	(11,714)	(33,533)	(34,900)
Amortization of net (gain) or loss and prior service costs	1,981	450	5,662	2,380
Net periodic benefit cost	(1,165)	(4,653)	(4,130)	(13,055)
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	25	(13)	75
Interest cost	160	77	525	230
Amortization of net (gain) or loss and prior service costs	(243)	(139)	(652)	(417)
Net periodic benefit cost	$ (75)	$ (37)	$ (140)	$ (112)