Investment Securities (Summary of Amortized Cost and Fair Value of Held-to-Maturity Investment Securities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Held-to-maturity Securities
Investment securities held-to-maturity, Amortized Cost	$ 316,413	$ 273,905
Investment securities held-to-maturity, Unrealized Gains	7,294	5,462
Investment securities held-to-maturity, Unrealized Losses	7,967	11,096
Held-to-maturity Securities, Fair Value	315,740	268,271
State and political subdivisions [Member]
Held-to-maturity Securities
Investment securities held-to-maturity, Amortized Cost	305,913	263,405
Investment securities held-to-maturity, Unrealized Gains	7,294	5,462
Investment securities held-to-maturity, Unrealized Losses	4,557	6,846
Held-to-maturity Securities, Fair Value	308,650	262,021
Trust preferred securities [Member]
Held-to-maturity Securities
Investment securities held-to-maturity, Amortized Cost	10,500	10,500
Investment securities held-to-maturity, Unrealized Gains	0	0
Investment securities held-to-maturity, Unrealized Losses	3,410	4,250
Held-to-maturity Securities, Fair Value	$ 7,090	$ 6,250

Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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- Definition

Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

+ References

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Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

+ References

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Fair value of investments in debt securities classified as held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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-Section 50

-Paragraph 5

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-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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-Section 50

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