Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 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 cost	11	$ 12
Interest cost	216	266
Expected return on plan assets	(761)	(819)
Amortization of net gain	0	0
Amortization of prior service credit	0	0
Net periodic benefit	(534)	(541)
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	22	19
Interest cost	44	54
Expected return on plan assets	(327)	(296)
Amortization of net gain	(228)	(166)
Amortization of prior service credit	(52)	(49)
Net periodic benefit	$ (541)	$ (438)