Accumulated Other Comprehensive Income (Schedule of Changes In Each Component of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 695,476	$ 693,750	$ 701,106	$ 657,983
Other comprehensive (loss) income, net of tax	(7,349)	(539)	(16,016)	24,650
Ending balance	677,296	691,359	677,296	691,359
Defined Benefit Pension Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(5,661)	(6,270)	(5,661)	(6,270)
Ending balance	(5,661)	(6,270)	(5,661)	(6,270)
Securities available-for-sale:
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	28,227	37,299	36,894	12,110
Other comprehensive (loss) income before reclassifications	(7,349)	(539)	(15,779)	23,497
Amounts reclassified from other comprehensive income	0	0	(237)	(44)
Reclassification of unrealized gains on held-to-maturity securities to available-for-sale		0		1,197
Other comprehensive (loss) income, net of tax	(7,349)	(539)	(16,016)	24,650
Ending balance	20,878	36,760	20,878	36,760
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	22,566	31,029	31,233	5,840
Other comprehensive (loss) income before reclassifications	(7,349)	(539)	(15,779)	23,497
Amounts reclassified from other comprehensive income	0	0	(237)	(44)
Reclassification of unrealized gains on held-to-maturity securities to available-for-sale		0		1,197
Other comprehensive (loss) income, net of tax	(7,349)	(539)	(16,016)	24,650
Ending balance	$ 15,217	$ 30,490	$ 15,217	$ 30,490