Pensions and Other Postretirement Benefit Plans (Schedule of Net Periodic Benefit Plan Cost) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Pension plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,630	$ 1,728
Interest cost	3,999	4,621
Expected return on assets	(4,802)	(5,139)
Settlement	0	145
Curtailment	0	233
Amortization of prior service cost/(credit)	10	24
Amortization of net actuarial loss	1,625	1,776
Net periodic benefit cost	2,462	3,388
Other postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	99	150
Interest cost	827	1,285
Expected return on assets	0	0
Settlement	0	0
Curtailment	0	0
Amortization of prior service cost/(credit)	(3,366)	(3,366)
Amortization of net actuarial loss	1,695	1,944
Net periodic benefit cost	$ (745)	$ 13