Pension Benefits and Other Postretirement Benefits (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0
Interest cost	231	1,784
Expected return of plan assets	(393)	(2,192)
Amortization of prior service credit	0	0
Amortization of net loss	114	454
Net periodic benefit (credit) cost	(48)	46
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	17	18
Interest cost	10	15
Expected return of plan assets	0	0
Amortization of prior service credit	(28)	(253)
Amortization of net loss	0	0
Net periodic benefit (credit) cost	$ (1)	$ (220)