Consolidated Statements 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	$ 62,210	$ 59,222	$ 46,529
Unrealized Gains (Losses) on Securities:
Unrealized Holding Gain (Loss) Arising During the Period	29,783	29,866	(4,936)
Reclassification Adjustment for Gains Included in Net Income	(4,081)	(1,248)	(706)
Tax Effect	(5,432)	(6,186)	1,218
Net of Tax	20,270	22,432	(4,424)
Postretirement Benefit Obligation:
Net (Loss) Arising During the Period	0	(310)	(73)
Reclassification Adjustment for Amortization of Prior Service Cost and Net Loss Included in Net Periodic Pension Cost	0	37	32
Tax Effect	0	44	(13)
Net of Tax	0	(229)	(54)
Comprehensive Income (Loss)	20,270	22,203	(4,478)
COMPREHENSIVE INCOME	$ 82,480	$ 81,425	$ 42,051