Pension Benefits and Other Postretirement Benefits (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Settlement benefit	$ 0	$ 0	$ 55	$ 0
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0
Interest cost	223	1,790	685	5,359
Expected return of plan assets	(394)	(2,187)	(1,180)	(6,571)
Amortization of prior service credit	0	0	0	0
Amortization of net loss	99	476	327	1,386
Settlement benefit	0	0	(63)	0
Net periodic benefit (credit) cost	(72)	79	(231)	174
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	17	12	51	48
Interest cost	10	14	30	44
Expected return of plan assets	0	0	0	0
Amortization of prior service credit	(28)	(252)	(84)	(758)
Amortization of net loss	0	0	0	0
Settlement benefit	0	0	0	0
Net periodic benefit (credit) cost	$ (1)	$ (226)	$ (3)	$ (666)