Pensions and Other Postretirement Benefit Plans (Schedule of Net Periodic Benefit Plan Cost) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,148	$ 1,261
Interest cost	3,071	3,578
Expected return on assets	(3,415)	(4,102)
Settlement cost	145	0
Curtailment cost	233	0
Amortization of prior service cost/(credit)	16	34
Amortization of net actuarial loss	1,180	1,125
Amortization of prior service cost/(credit)	2,378	1,896
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	100	95
Interest cost	857	1,057
Expected return on assets	0	0
Settlement cost	0	0
Curtailment cost	0	0
Amortization of prior service cost/(credit)	(2,244)	(2,244)
Amortization of net actuarial loss	1,296	1,114
Amortization of prior service cost/(credit)	$ 9	$ 22