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 (Loss) Attributable to Parent	$ 89,595	$ 89,352	$ 70,002
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, Portion Attributable to Parent [Abstract]
Unrealized gain (loss) on available-for-sale securities arising during period	31,157	27,115	(7,054)
Reclassification adjustment for net (gains) losses	(62)	(69)	90
OCI, Debt Securities, Available-for-Sale, Transfer from Held-to-Maturity, Gain (Loss), before Adjustment and Tax	1,562	0	0
Other comprehensive income (loss) related to available-for-sale securities	32,657	27,046	(6,964)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Tax, after Reclassification Adjustment, Attributable to Parent [Abstract]
Amortization of actuarial net gains	1,089	917	890
Recognition of unrealized losses	(352)	(1,447)	(1,982)
Change in underfunded pension liability	737	(530)	(1,092)
Other comprehensive income (loss) before income taxes	33,394	26,516	(8,056)
Tax effect	(8,001)	(6,194)	1,875
Other comprehensive income (loss), net of tax	25,393	20,322	(6,181)
Comprehensive income, net of tax	$ 114,988	$ 109,674	$ 63,821