Pensions and Other Postretirement Benefit Plans (Schedule of Net Periodic Benefit Plan Cost) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,728	$ 1,892
Interest cost	4,621	5,368
Expected return on assets	(5,139)	(6,155)
Settlement cost	145	0
Curtailment cost	233	0
Amortization of prior service cost/(credit)	24	51
Amortization of net actuarial loss	1,776	1,687
Amortization of prior service cost/(credit)	3,388	2,843
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	150	142
Interest cost	1,285	1,585
Expected return on assets	0	0
Settlement cost	0	0
Curtailment cost	0	0
Amortization of prior service cost/(credit)	(3,366)	(3,366)
Amortization of net actuarial loss	1,944	1,670
Amortization of prior service cost/(credit)	$ 13	$ 31