Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	$ 1,229,099	$ 1,258,676
Carrying Value [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	1,229,099
Carrying Value [Member] \| U.S. Treasury [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	2,005
Carrying Value [Member] \| U.S. Government Sponsored Enterprises [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	85,369
Carrying Value [Member] \| SBA Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	8,255
Carrying Value [Member] \| U.S. Government Agency and Sponsored Mortgage Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	1,062,081
Carrying Value [Member] \| Privately Issued Residential Mortgage Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	3,083
Carrying Value [Member] \| Obligations Issued by States and Political Subdivisions [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	65,469
Carrying Value [Member] \| Other Debt Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	2,264
Carrying Value [Member] \| Equity Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	573
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	231
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] \| U.S. Treasury [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] \| U.S. Government Sponsored Enterprises [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] \| SBA Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] \| U.S. Government Agency and Sponsored Mortgage Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] \| Privately Issued Residential Mortgage Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] \| Obligations Issued by States and Political Subdivisions [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] \| Other Debt Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] \| Equity Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	231
Significant Observable Inputs (Level 2) [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	1,164,807
Significant Observable Inputs (Level 2) [Member] \| U.S. Treasury [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	2,005
Significant Observable Inputs (Level 2) [Member] \| U.S. Government Sponsored Enterprises [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	85,369
Significant Observable Inputs (Level 2) [Member] \| SBA Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	8,255
Significant Observable Inputs (Level 2) [Member] \| U.S. Government Agency and Sponsored Mortgage Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	1,062,081
Significant Observable Inputs (Level 2) [Member] \| Privately Issued Residential Mortgage Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	3,083
Significant Observable Inputs (Level 2) [Member] \| Obligations Issued by States and Political Subdivisions [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	1,750
Significant Observable Inputs (Level 2) [Member] \| Other Debt Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	2,264
Significant Observable Inputs (Level 2) [Member] \| Equity Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Significant Other Unobservable Inputs (Level 3) [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	64,061
Significant Other Unobservable Inputs (Level 3) [Member] \| U.S. Treasury [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Significant Other Unobservable Inputs (Level 3) [Member] \| U.S. Government Sponsored Enterprises [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Significant Other Unobservable Inputs (Level 3) [Member] \| SBA Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Significant Other Unobservable Inputs (Level 3) [Member] \| U.S. Government Agency and Sponsored Mortgage Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Significant Other Unobservable Inputs (Level 3) [Member] \| Privately Issued Residential Mortgage Backed Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Significant Other Unobservable Inputs (Level 3) [Member] \| Obligations Issued by States and Political Subdivisions [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	63,719
Significant Other Unobservable Inputs (Level 3) [Member] \| Other Debt Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total
Significant Other Unobservable Inputs (Level 3) [Member] \| Equity Securities [Member]
Financial Instruments Measured at Fair Value on a Recurring Basis
Available-for-sale securities, Total	$ 342

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-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.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-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.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

-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.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7534914&loc=d3e22054-111558

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15E

-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.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-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.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 14

-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.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

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