Securities - (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Amortized cost and fair value of securities held to maturity
Amortized Cost	$ 448,376	$ 458,400
Gross Unrealized Gains	18,208	16,662
Gross Unrealized Losses	(524)	(1,309)
Fair Value	466,060	473,753
Obligations of other U.S. Government agencies and corporations
Amortized cost and fair value of securities held to maturity
Amortized Cost	93,498	101,155
Gross Unrealized Gains	58	26
Gross Unrealized Losses	(505)	(1,214)
Fair Value	93,051	99,967
Obligations of states and political subdivisions
Amortized cost and fair value of securities held to maturity
Amortized Cost	354,878	357,245
Gross Unrealized Gains	18,150	16,636
Gross Unrealized Losses	(19)	(95)
Fair Value	$ 373,009	$ 373,786

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

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

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

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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=73527792&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

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