Defined Benefit Post-Retirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Employee Benefit Plans [Abstract]
Employer contributions	$ 0	$ 0	$ 0	$ 0
Pension Benefits [Member]
Components of net periodic (benefit) cost [Abstract]
Service cost	485	446	970	892
Interest cost	677	809	1,354	1,618
Expected return on plan assets	(2,203)	(2,105)	(4,406)	(4,210)
Net amortization	313	368	626	736
Net periodic pension (benefit) cost	(728)	(482)	(1,456)	(964)
Other Benefits [Member]
Components of net periodic (benefit) cost [Abstract]
Service cost	2	2	4	4
Interest cost	45	55	90	110
Expected return on plan assets	0	0	0	0
Net amortization	13	13	26	26
Net periodic pension (benefit) cost	$ 60	$ 70	$ 120	$ 140