Pensions and Other Postretirement Benefit Plans (Schedule of Net Periodic Benefit Plan Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain	$ 2	$ 5		$ 70
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost			$ 1,892	2,085
Interest cost			5,368	5,430
Expected return on assets			(6,155)	(6,702)
Curtailment gain				(750)
Amortization of prior service cost/(credit)			51	25
Amortization of net actuarial loss			1,687	1,665
Net periodic benefit cost			2,843	1,753
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost			142	174
Interest cost			1,585	1,520
Expected return on assets
Curtailment gain
Amortization of prior service cost/(credit)			(3,366)	(3,366)
Amortization of net actuarial loss			1,670	2,217
Net periodic benefit cost			$ 31	$ 545