Pension and Other Postretirement Benefits - The Components of the Net Pension Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Employee Pension Plan [Member]
Interest cost	$ 163	$ 199	$ 326	$ 398
Amortization of unrecognized (gain) loss	111	66	222	133
Expected return on plan assets	(257)	(272)	(514)	(544)
Net pension (benefit) expense	17	(7)	34	(13)
Directors' Plan [Member]
Service cost	3	10	7	20
Interest cost	16	21	32	42
Amortization of unrecognized (gain) loss	(13)	(35)	(27)	(70)
Amortization of past service credit	0	0	0	0
Net pension (benefit) expense	6	(4)	12	(8)
Other Post Retirement Benefit Plan Defined Benefit [Member]
Service cost	68	70	137	140
Interest cost	65	85	130	170
Amortization of past service credit	(23)	(20)	(43)	(42)
Net pension (benefit) expense	$ 110	$ 135	$ 224	$ 268