Pension Benefits and Other Postretirement Benefits (Components of Net Periodic Benefit (Credit) Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0
Interest cost	184	231
Expected return of plan assets	(390)	(393)
Amortization of prior service credit	0	0
Amortization of net loss	98	114
Net periodic benefit (credit) cost	(108)	(48)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	15	17
Interest cost	6	10
Expected return of plan assets	0	0
Amortization of prior service credit	(24)	(28)
Amortization of net loss	0	0
Net periodic benefit (credit) cost	$ (3)	$ (1)