Pension and Other Postretirement Benefits - The Components of the Net Pension Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Employee Pension Plan [Member]
Interest cost	$ 163	$ 199	$ 489	$ 597
Amortization of unrecognized (gain) loss	111	68	333	201
Expected return on plan assets	(257)	(272)	(771)	(816)
Net pension (benefit) expense	17	(5)	51	(18)
Directors' Plan [Member]
Service cost	4	10	11	30
Interest cost	16	21	48	63
Amortization of unrecognized (gain) loss	(14)	(35)	(41)	(105)
Amortization of past service credit	0	0	0	0
Net pension (benefit) expense	6	(4)	18	(12)
Other Post Retirement Benefit Plan Defined Benefit [Member]
Service cost	69	70	206	210
Interest cost	64	85	194	255
Amortization of past service credit	(21)	(22)	(64)	(64)
Net pension (benefit) expense	$ 112	$ 133	$ 336	$ 401