Pension and Postretirement Benefit Plans - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SERP I and SERP II
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0
Interest cost	160	176	184
Amortization of prior service cost	0	0	0
Recognition of net actuarial loss	70	59	57
Net periodic pension cost	$ 230	$ 235	$ 241
Discount Rate Used in the Calculation of Periodic Pension Costs	3.30%	3.75%	3.90%
PRBP
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0
Interest cost	9	11	17
Amortization of prior service cost	0	0	0
Recognition of net actuarial loss	30	36	41
Net periodic pension cost	$ 39	$ 47	$ 58
Discount Rate Used in the Calculation of Periodic Pension Costs	2.75%	2.80%	3.90%