Securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Amortized cost and fair value of securities held to maturity
Amortized Cost, Held to Maturity	$ 299,139	$ 332,410
Gross Unrealized Gains, Held to Maturity	17,645	12,308
Gross Unrealized Losses, Held to Maturity	(86)	(100)
Fair Value, Held to Maturity	316,698	344,618
Obligations of other U.S. Government agencies and corporations [Member]
Amortized cost and fair value of securities held to maturity
Amortized Cost, Held to Maturity	66,916	107,660
Gross Unrealized Gains, Held to Maturity	105	225
Gross Unrealized Losses, Held to Maturity	(57)	(74)
Fair Value, Held to Maturity	66,964	107,811
Obligations of states and political subdivisions [Member]
Amortized cost and fair value of securities held to maturity
Amortized Cost, Held to Maturity	232,223	224,750
Gross Unrealized Gains, Held to Maturity	17,540	12,083
Gross Unrealized Losses, Held to Maturity	(29)	(26)
Fair Value, Held to Maturity	$ 249,734	$ 236,807

This item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.

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As of the balance sheet date, the excess of fair value over carrying value (amortized cost) of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding gain.

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- Definition

As of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss.

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