Investment in Securities (Schedule of Investment Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Fair Value	$ 427,244	$ 357,726
Gross Unrealized Gains	16,301	19,679
Gross Unrealized Losses	885
Amortized Cost	411,828	338,047
State and political subdivisions [Member]
Marketable Securities [Line Items]
Fair Value	327,983	305,974
Gross Unrealized Gains	15,678	18,915
Gross Unrealized Losses	174
Amortized Cost	312,479	287,059
U.S. government agencies [Member]
Marketable Securities [Line Items]
Fair Value	99,261	51,752
Gross Unrealized Gains	623	764
Gross Unrealized Losses	711
Amortized Cost	$ 99,349	$ 50,988

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

No definition available.

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- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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