Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 36,279	$ 29,326	$ 26,534
Other Comprehensive Income (Loss), Net of Tax:
Unrealized Net Securities Holding Losses Arising During the Year	(2,116)	(940)	(1,024)
Reclassification Adjustment for Net Securities Losses Included in Net Income	0	337	13
Net Retirement Plan (Loss) Gain	(2,833)	214	1,721
Net Retirement Plan Prior Service (Cost) Credit	(338)	0	0
Amortization of Net Retirement Plan Actuarial Loss	242	362	435
Amortization of Net Retirement Plan Prior Service (Credit) Cost	80	(8)	(7)
Other Comprehensive Income (Loss)	(4,965)	(35)	1,138
Comprehensive Income	$ 31,314	$ 29,291	$ 27,672