Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 40,827	$ 37,475	$ 36,279
Other Comprehensive Income (Loss), Net of Tax:
Unrealized Net Securities Holding Gains (Losses) Arising During the Year	5,306	4,162	(2,116)
Reclassification Adjustment for Net Securities Losses Arising During the the Year	28	0	0
Net Unrealized Gains on Cash Flow Hedge Agreements	485	0
Net Retirement Plan (Loss) Gain	(251)	2,614	(2,833)
Net Retirement Plan Prior Service Cost	(353)	0	(338)
Amortization of Net Retirement Plan Actuarial Loss	169	510	242
Amortization of Net Retirement Plan Prior Service Cost	157	167	80
Other Comprehensive Income (Loss)	5,541	7,453	(4,965)
Comprehensive Income	$ 46,368	$ 44,928	$ 31,314