| **Investment Securities - Amortized Cost and Fair Value of Available for Sale Securities and Held to Maturity Securities by Contractual Maturity (Details) (USD $)In Thousands, unless otherwise specified** | Sep. 30, 2013 | Dec. 31, 2012 |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Available for Sale**                                                                                                                                                                                       |          |          |
| Due in one year or less - Amortized Cost                                                                                                                                                                     | $ 8,404       |          |
| Due after one through five years - Amortized Cost                                                                                                                                                            | 11,972        |          |
| Due after five through ten years - Amortized Cost                                                                                                                                                            | 57,708        |          |
| Due after ten years - Amortized Cost                                                                                                                                                                         | 132,704       |          |
| Total debt securities with a single maturity date - Amortized Cost                                                                                                                                           | 210,788       |          |
| Total Investment Securities - Amortized Cost                                                                                                                                                                 | 610,181       |          |
| Due in one year or less - Fair Value                                                                                                                                                                         | 8,591         |          |
| Due after one through five years - Fair Value                                                                                                                                                                | 12,481        |          |
| Due after five through ten years - Fair Value                                                                                                                                                                | 59,110        |          |
| Due after ten years - Fair Value                                                                                                                                                                             | 126,284       |          |
| Total debt securities with a single maturity date - Fair Value                                                                                                                                               | 206,466       |          |
| Total Investment Securities - Fair Value                                                                                                                                                                     | 606,341       |          |
| **Held to Maturity**                                                                                                                                                                                         |          |          |
| Due in one year or less - Amortized Cost                                                                                                                                                                     | 1,060         |          |
| Due after one through five years - Amortized Cost                                                                                                                                                            | 13,116        |          |
| Due after five through ten years - Amortized Cost                                                                                                                                                            | 59,473        |          |
| Due after ten years - Amortized Cost                                                                                                                                                                         | 42,147        |          |
| Total debt securities with a single maturity date - Amortized Cost                                                                                                                                           | 115,796       |          |
| Total Investment Securities - Amortized Cost                                                                                                                                                                 | 307,794       | 361,020       |
| Due in one year or less - Fair Value                                                                                                                                                                         | 1,061         |          |
| Due after one through five years - Fair Value                                                                                                                                                                | 13,324        |          |
| Due after five through ten years - Fair Value                                                                                                                                                                | 59,634        |          |
| Due after ten years - Fair Value                                                                                                                                                                             | 42,269        |          |
| Total debt securities with a single maturity date - Fair Value                                                                                                                                               | 116,288       |          |
| Investment securities held to maturity - fair value                                                                                                                                                          | 314,383       | 378,174       |
| U.S. Government-sponsored mortgage-backed securities                                                                                                                                                         |          |          |
| **Available for Sale**                                                                                                                                                                                       |          |          |
| Without single maturity date - Amortized Cost                                                                                                                                                                | 397,687       |          |
| Without single maturity date - Fair Value                                                                                                                                                                    | 398,169       |          |
| **Held to Maturity**                                                                                                                                                                                         |          |          |
| Without single maturity date - Amortized Cost                                                                                                                                                                | 191,998       |          |
| Total Investment Securities - Amortized Cost                                                                                                                                                                 | 191,998       | 243,793       |
| Without single maturity date - Fair Value                                                                                                                                                                    | 198,095       |          |
| Investment securities held to maturity - fair value                                                                                                                                                          | 198,095       | 255,459       |
| Equity securities                                                                                                                                                                                            |          |          |
| **Available for Sale**                                                                                                                                                                                       |          |          |
| Without single maturity date - Amortized Cost                                                                                                                                                                | 1,706         |          |
| Without single maturity date - Fair Value                                                                                                                                                                    | $ 1,706       |          |

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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| - Definition
Amount of available-for-sale debt securities at cost, net of adjustments, that do not have a single maturity date and which the entity has decided to disclose separately rather than allocating the cost over several maturity groupings. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.
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Amount of debt securities categorized neither as held-to-maturity nor trading.
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Amount after 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.
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