Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 59,222	$ 46,529	$ 40,676
Unrealized Gains (Losses) on Securities:
Unrealized Holding Gain (Loss) Arising During the Period	29,866	(4,936)	7,364
Reclassification Adjustment for Gains Included in Net Income	(1,248)	(706)	(596)
Tax Effect	(6,186)	1,218	(2,377)
Net of Tax	22,432	(4,424)	4,391
Postretirement Benefit Obligation:
Net (Loss) Arising During the Period	(310)	(73)	(226)
Reclassification Adjustment for Amortization of Prior Service Cost and Net Loss Included in Net Periodic Pension Cost	37	32	8
Tax Effect	44	(13)	80
Net of Tax	(229)	(54)	(138)
Total Other Comprehensive Income (Loss)	22,203	(4,478)	4,253
COMPREHENSIVE INCOME	$ 81,425	$ 42,051	$ 44,929