Pension Benefits and Other Postretirement Benefits (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Settlement benefit	$ 55	$ 0	$ 55	$ 0
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0
Interest cost	231	1,785	462	3,569
Expected return of plan assets	(393)	(2,192)	(786)	(4,384)
Amortization of prior service credit	0	0	0	0
Amortization of net loss	114	456	228	910
Settlement benefit	(63)	0	(63)	0
Net periodic benefit (credit) cost	(111)	49	(159)	95
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	17	18	34	36
Interest cost	10	15	20	30
Expected return of plan assets	0	0	0	0
Amortization of prior service credit	(28)	(253)	(56)	(506)
Amortization of net loss	0	0	0	0
Settlement benefit	0	0	0	0
Net periodic benefit (credit) cost	$ (1)	$ (220)	$ (2)	$ (440)