Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Components of net periodic benefit cost [Abstract]
Contribution made to pension and postretirement plans			$ 0
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service (credit) cost	$ (11)	$ 7	0	$ 19
Interest cost	212	272	428	538
Expected return on plan assets	(662)	(691)	(1,423)	(1,510)
Amortization of net loss (gain)	0	5	0	5
Amortization of prior service cost (credit)	0	0	0	0
Net periodic benefit	(461)	(407)	(995)	(948)
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service (credit) cost	26	21	48	40
Interest cost	39	58	83	112
Expected return on plan assets	(290)	(296)	(617)	(592)
Amortization of net loss (gain)	(169)	(148)	(397)	(314)
Amortization of prior service cost (credit)	102	(49)	50	(98)
Net periodic benefit	$ (292)	$ (414)	$ (833)	$ (852)