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Investments and Fair Value Measurements (Tables) | 12 Months Ended
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Dec. 31, 2012
Investments and Fair Value Measurements [Abstract] |
Schedule of Available-for-sale Securities Reconciliation [Table Text Block] | The amortized cost and fair value of available-for-sale investments at December 31, 2012 and December 31, 2011 were as follows:
|  |  |  | Gross |  | Gross |  |
|  | Amortized |  | Unrealized |  | Unrealized |  | Fair
|  | Cost |  | Gains |  | Losses |  | Value
|  | ( in thousands)
December 31, 2012 |  |
Long-term: |  |  |  |  |  |  |  |  |  |  |  |
Auction rate student loan educational bonds |  | $ | 21,300 |  |  | $ | — |  |  | $ | 1,284 |  |  | $ | 20,016 |
December 31, 2011 |  |  |  |  |  |  |  |
Long-term: |  |  |  |  |  |  |  |  |  |  |  |
Auction rate student loan educational bonds |  | $ | 53,650 |  |  | $ | — |  |  | $ | 3,081 |  |  | $ | 50,569 |
Investments Classified by Contractual Maturity Date [Table Text Block] |
|  | Fair Value |  | Amortized Cost
Due within one year |  | $ | 25 |  |  | $ | 25 |
Due after one year through five years |  | — |  |  | — |
Due after five years through ten years |  | — |  |  | — |
Due after ten years through May 1, 2040 |  | 19,991 |  |  | 21,275 |
|  | $ | 20,016 |  |  | $ | 21,300 |
Schedule of Inputs Used in Securities Models [Table Text Block] |
| December 31, 2012 |  | December 31, 2011
Average life of underlying loans | 2-12 years |  | 2-12 years
Rate of return | 0.42-2.11% |  | 0.68-2.92%
Discount rate | 0.25-0.84% |  | 0.48-1.14%
Liquidity discount rate | 0.17-0.61% |  | 0.55-1.16%
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] | The table below presents a rollforward for all assets and liabilities, measured at fair value, on a recurring basis using significant unobservable inputs (Level 3) during the years ended December 31, 2012 and 2011.
|  | Available-for-sale debt securities
|  | (in thousands)
|  | 2012 |  | 2011
Balance, January 1 |  | $ | 50,569 |  |  | $ | 88,694 |
Settlements |  | (32,350 | ) |  | (38,125 | )
Purchases |  | — |  |  | — |
Issuances |  | — |  |  | — |
Sales |  | — |  |  | — |
Transfers in to (out of) Level 3 |  | — |  |  | — |
Total gains or losses (realized/unrealized): |  |  |  |  |
Included in earnings |  | — |  |  | — |
Included in other comprehensive income, net of tax |  | 1,797 |  |  | — |
Balance, December 31, |  | $ | 20,016 |  |  | $ | 50,569 |

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