Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Employee Benefits	$ 10,383	$ 9,319
INCOME BEFORE PROVISION FOR INCOME TAXES	10,174	10,884
Provision for income taxes	(2,047)	(2,150)
Net Income	8,127	8,734
Reclassification out of Accumulated Other Comprehensive Income
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net Income	(66)	(163)
Reclassification out of Accumulated Other Comprehensive Income | Accretion of Net Retirement Plan Prior Service (Cost) Credit
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Employee Benefits	(54)	(56)
Reclassification out of Accumulated Other Comprehensive Income | Amortization of Net Retirement Plan Actuarial Gain (Loss)
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Employee Benefits	(36)	(163)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
INCOME BEFORE PROVISION FOR INCOME TAXES	(90)	(219)
Provision for income taxes	24	56
Net Income	$ (66)	$ (163)