Comprehensive Income - Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ 2,871	$ 2,576	$ 8,171	$ 5,583
Other comprehensive income (loss), tax	(735)	(656)	(2,090)	(1,420)
Other Comprehensive Income	2,136	1,920	6,081	4,163
Unrealized Gains and Losses on Available for Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	2,716	2,340	8,220	5,128
Other comprehensive income (loss), tax	(695)	(596)	(2,101)	(1,304)
Other Comprehensive Income	2,021	1,744	6,119	3,824
Unrealized Loss on Cash Flow Swap
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	25		(269)
Other comprehensive income (loss), tax	(7)		68
Other Comprehensive Income	18	0	(201)	0
Amortization of Net Retirement Plan Actuarial Gain (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	78	179	114	342
Other comprehensive income (loss), tax	(20)	(46)	(29)	(88)
Other Comprehensive Income	58	133	85	254
Accumulated Defined Benefit Plans Adjustment, Net Prior Service
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	52	57	106	113
Other comprehensive income (loss), tax	(13)	(14)	(28)	(28)
Other Comprehensive Income	$ 39	$ 43	$ 78	$ 85