Investment Securities (Summary of Amortized Cost and Fair Value of Held-to-Maturity Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Investment Securities Held-to-Maturity
Amortized Cost	$ 624,099	$ 677,093
Unrealized Gains	2,548	3,856
Unrealized Losses	7,975	18,043
Fair Value	618,672	662,906
State and political subdivisions
Investment Securities Held-to-Maturity
Amortized Cost	623,599	676,593
Unrealized Gains	2,548	3,856
Unrealized Losses	7,915	17,933
Fair Value	618,232	662,516
Trust preferred securities
Investment Securities Held-to-Maturity
Amortized Cost	500	500
Unrealized Gains	0	0
Unrealized Losses	60	110
Fair Value	$ 440	$ 390

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- Definition

Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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- Definition

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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- Definition

Amount, before other-than-temporary impairment (OTTI) accretion, of investment in debt securities measured at amortized cost (held-to-maturity).

+ References

No definition available.

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- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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