| **Investment Securities Amortized Cost and Estimated Fair Value of Held to Maturity Securities (Details) (USD $)In Thousands, unless otherwise specified** | Mar. 31, 2015                                                                                                                                                    | Dec. 31, 2014                                                                                                                                                    | Mar. 31, 2014                                                                                                                                                   |
|------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|
| **Schedule of Held-to-maturity Securities [Line Items]**                                                                                                   |                                                                                                                                                             |                                                                                                                                                             |                                                                                                                                                            |
| Amortized Cost                                                                                                                                             | $ 262,455us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment                                                                         | $ 275,919us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment                                                                         | $ 182,853us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment                                                                        |
| Unrealized Gains                                                                                                                                           | 5,949us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain                                                                                          | 5,998us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain                                                                                          | 3,724us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain                                                                                         |
| Unrealized Losses                                                                                                                                          | (1,157)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss                                                                                        | (2,213)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss                                                                                        | (10,015)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss                                                                                      |
| Fair Value (Estimated)                                                                                                                                     | 267,247us-gaap_HeldToMaturitySecuritiesFairValue                                                                                                                 | 279,704us-gaap_HeldToMaturitySecuritiesFairValue                                                                                                                 | 176,562us-gaap_HeldToMaturitySecuritiesFairValue                                                                                                                |
| U.S. Government-sponsored agencies                                                                                                                         |                                                                                                                                                             |                                                                                                                                                             |                                                                                                                                                            |
| **Schedule of Held-to-maturity Securities [Line Items]**                                                                                                   |                                                                                                                                                             |                                                                                                                                                             |                                                                                                                                                            |
| Amortized Cost                                                                                                                                             | 82,974us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember           | 92,341us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember           | 92,312us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember          |
| Unrealized Gains                                                                                                                                           | 108us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember                           | 54us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember                            | 2us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember                            |
| Unrealized Losses                                                                                                                                          | (912)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember                         | (2,066)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember                       | (9,131)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember                      |
| Fair Value (Estimated)                                                                                                                                     | 82,170us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember                                                 | 90,329us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember                                                 | 83,183us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_USTreasuryAndGovernmentMember                                                |
| Mortgage-backed securities                                                                                                                                 |                                                                                                                                                             |                                                                                                                                                             |                                                                                                                                                            |
| **Schedule of Held-to-maturity Securities [Line Items]**                                                                                                   |                                                                                                                                                             |                                                                                                                                                             |                                                                                                                                                            |
| Amortized Cost                                                                                                                                             | 53,228us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember          | 57,003us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember          | 49,805us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember         |
| Unrealized Gains                                                                                                                                           | 2,030us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember                        | 1,830us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember                        | 1,652us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember                       |
| Unrealized Losses                                                                                                                                          | (116)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember                        | (116)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember                        | (789)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember                       |
| Fair Value (Estimated)                                                                                                                                     | 55,142us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember                                                | 58,717us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember                                                | 50,668us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_MortgageBackedSecuritiesMember                                               |
| State and political subdivisions                                                                                                                           |                                                                                                                                                             |                                                                                                                                                             |                                                                                                                                                            |
| **Schedule of Held-to-maturity Securities [Line Items]**                                                                                                   |                                                                                                                                                             |                                                                                                                                                             |                                                                                                                                                            |
| Amortized Cost                                                                                                                                             | 125,953us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember | 126,275us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember | 40,436us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember |
| Unrealized Gains                                                                                                                                           | 3,811us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                | 4,114us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                | 2,070us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember               |
| Unrealized Losses                                                                                                                                          | (129)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                | (31)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                 | (95)us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                |
| Fair Value (Estimated)                                                                                                                                     | 129,635us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                                       | 130,358us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                                       | 42,411us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                                       |
| Corporate securities                                                                                                                                       |                                                                                                                                                             |                                                                                                                                                             |                                                                                                                                                            |
| **Schedule of Held-to-maturity Securities [Line Items]**                                                                                                   |                                                                                                                                                             |                                                                                                                                                             |                                                                                                                                                            |
| Amortized Cost                                                                                                                                             | 300us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember              | 300us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember              | 300us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember             |
| Unrealized Gains                                                                                                                                           | 0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember                             | 0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember                             | 0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember                            |
| Unrealized Losses                                                                                                                                          | 0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember                             | 0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember                             | 0us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember                            |
| Fair Value (Estimated)                                                                                                                                     | $ 300us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember                                                  | $ 300us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember                                                  | $ 300us-gaap_HeldToMaturitySecuritiesFairValue/ us-gaap_DebtSecurityAxis= us-gaap_CorporateDebtSecuritiesMember                                                 |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
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| - Definition
Amount of accumulated unrealized gain on 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 (b) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of accumulated unrealized loss on 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 (c) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563
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| X                                                                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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=27724398&loc=d3e27232-111563Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563
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