Investment in Securities (Schedule of Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Fair Value	$ 390,552	$ 375,696
Gross Unrealized Gains	5,239	12,552
Gross Unrealized Losses	3,731	13
Amortized Cost	389,044	363,157
State and Political Subdivisions [Member]
Investment [Line Items]
Fair Value	370,134	369,070
Gross Unrealized Gains	5,239	12,552
Gross Unrealized Losses	3,328	13
Amortized Cost	368,223	356,531
U.S. government agencies [Member]
Investment [Line Items]
Fair Value	12,672
Gross Unrealized Gains
Gross Unrealized Losses	403
Amortized Cost	13,075
Certificates of Deposit [Member]
Investment [Line Items]
Fair Value	7,746	6,626
Gross Unrealized Gains
Gross Unrealized Losses
Amortized Cost	$ 7,746	$ 6,626

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
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-Publisher FASB
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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Paragraph 2
-Subparagraph (c)
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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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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
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