Pensions and Other Postretirement Benefit Plans (Schedule of Net Periodic Benefit Plan Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 580	$ 632
Interest cost	1,550	1,794
Expected return on assets	(1,723)	(2,057)
Amortization of prior service cost/(credit)	8	17
Amortization of net actuarial loss	596	564
Net periodic benefit cost	1,011	950
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	50	47
Interest cost	428	528
Expected return on assets
Amortization of prior service cost/(credit)	(1,122)	(1,122)
Amortization of net actuarial loss	648	557
Net periodic benefit cost	$ 4	$ 10