Investment Securities (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
Sep. 30, 2011 securities	Sep. 30, 2010	Dec. 31, 2010
Investment Securities [Abstract]
Amount of securities pledged to secure public funds and other purposes as required by law	$ 1,799,101		$ 1,561,964
Number of non-agency residential mortgage-backed securities that have subprime or Alt-A components	0
Number of non-agency residential mortgage backed securities	13
Number of non-agency residential mortgage backed securities in a loss position	0
Number of non-agency residential mortgage backed securities rated below investment grade	7
Number of non-agency residential mortgage backed securities with other-than-temporary impairment	4
Non-credit related unrealized loss on other-than-temporarily impaired debt securities, net of taxes		$ (599)
Minimum default recovery rate	10.00%
Minimum Texas ratio for recoveries not forecasted	250.00%
Number of securities in unrealized loss positions	8
Number of securities	12
Number of securities in unrealized loss position rated below investment grade	1

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- Definition

Minimum Texas Ratio Used To Determine That No Recoveries Of Issue In Default Will Be Forecasted

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- Definition

Number of nonagency residential mortgage-backed securities determined to be other-than-temporarily impaired.

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- Definition

Non-agency Residential Mortgage-backed Securities, Number of Securities

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- Definition

Number of non-agency residential mortgage-backed securities that have subprime or Alt-A components.

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Non Agency Residential Mortgage Backed Securities Number Of Securities In Loss Position

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- Definition

Non-agency Residential Mortgage Backed Securities, Number of Securities Rated Below Investment Grade

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- Definition

Other Debt Securities, Number of Securities

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- Definition

Other Debt Securities, Number of Securities in Unrealized Loss Positions

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Other Debt Securities, Number of Securities in Unrealized Loss Positions Rated Below Investment Grade

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- Definition

The carrying value of securities pledged to secure public funds and for other purposes as required by law.

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- Definition

The after-tax amount of other than temporary impairment (OTTI) loss on a debt security, categorized as Available-for-sale, related to factors other than credit losses when the entity does not intend to sell the security and it is not more likely than not that the entity will be required to sell the security before recovery of its amortized cost basis. This amount of other than temporary losses on Available-for-sale Securities, net of applicable taxes, includes the portion attributable to the noncontrolling interest, if any; this amount is also referred to as the amount incurred by the reporting entity or the consolidated entity.

+ References

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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