Pensions and Other Postretirement Benefits (Components of Net Periodic Cost of Pension and Other Postretirement Benefit Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ 643	$ 1,682	$ 863
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Annual service cost	336	498	548
Less: employee contributions	0	21	35
Net service cost	336	477	513
Interest cost	620	686	674
Expected return on plan assets	(517)	(549)	(536)
Amortization of actuarial losses	202	507	463
Amortization of transition obligation	1	1	1
Curtailment and settlement losses	0	708	0
Net periodic benefit cost	642	1,830	1,115
OPEB Plans
Defined Benefit Plan Disclosure [Line Items]
Annual service cost	126	108	96
Less: employee contributions	0	0	0
Net service cost	126	108	96
Interest cost	180	152	142
Expected return on plan assets	0	0	0
Amortization of actuarial losses	156	177	119
Amortization of transition obligation	0	0	0
Curtailment and settlement losses	0	0	0
Net periodic benefit cost	$ 462	$ 437	$ 357