| **Long Term Debt (Schedule of Long Term Debt) (Details) (USD $)In Thousands, unless otherwise specified** | Dec. 31, 2012 | Dec. 31, 2011 |
|-----------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Debt Instrument [Line Items]**                                                                          |          |          |
| Long-term Debt, Gross                                                                                     | $ 879,794     | $ 864,288     |
| Debt Instrument, Unamortized Discount                                                                     | 2,743         |          |
| Long-term Debt, Current Maturities                                                                        | 1,928         | 3,241         |
| Long Term Debt, net                                                                                       | 875,123       | 858,031       |
| Senior Credit Facility [Member]                                                                           |          |          |
| **Debt Instrument [Line Items]**                                                                          |          |          |
| Long-term Debt                                                                                            | 90,000        | 60,000        |
| 2019 Notes [Member]                                                                                       |          |          |
| **Debt Instrument [Line Items]**                                                                          |          |          |
| Long-term Debt                                                                                            | 425,000       | 425,000       |
| Debt Instrument, Unamortized Discount                                                                     | 2,743         | 3,016         |
| 2021 Notes [Member]                                                                                       |          |          |
| **Debt Instrument [Line Items]**                                                                          |          |          |
| Long-term Debt                                                                                            | 325,000       | 325,000       |
| CoBank Mortgage [Member]                                                                                  |          |          |
| **Debt Instrument [Line Items]**                                                                          |          |          |
| Long-term Debt                                                                                            | 797           | 1,344         |
| Rural Utility Service [Member]                                                                            |          |          |
| **Debt Instrument [Line Items]**                                                                          |          |          |
| Long-term Debt                                                                                            | $ 38,997      | $ 52,944      |

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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.
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| - Definition
Carrying amount of long-term debt, net of unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.
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| - Definition
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