Investment in Securities (Schedule of Investment Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Investment [Line Items]
Fair Value	$ 441,189	$ 441,534
Gross Unrealized Gains	8,783	3,877
Gross Unrealized Losses	1,001	3,223
Amortized Cost	433,407	440,880
State and Political Subdivisions [Member]
Investment [Line Items]
Fair Value	335,543	334,717
Gross Unrealized Gains	8,585	3,791
Gross Unrealized Losses	181	1,806
Amortized Cost	327,139	332,732
U.S. government agencies [Member]
Investment [Line Items]
Fair Value	103,651	104,822
Gross Unrealized Gains	198	86
Gross Unrealized Losses	820	1,417
Amortized Cost	104,273	106,153
Certificates of Deposit [Member]
Investment [Line Items]
Fair Value	1,995	1,995
Gross Unrealized Gains
Gross Unrealized Losses
Amortized Cost	$ 1,995	$ 1,995

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- Definition

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

+ References

No definition available.

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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=118939692&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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