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Investments (Tables) | 12 Months Ended
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Dec. 31, 2011
Investments |
Summary of the amortized cost and estimated fair value of short-term investments for both available-for-sale and trading securities |
|  | 2011 |  | 2010 |
|  | Amortized |  | Fair |  | Amortized |  | Fair |
(Thousands of dollars) |  | Cost |  | Value |  | Cost |  | Value |
Money market funds |  | $ | 139,420 |  | $ | 139,420 |  | $ | 110,164 |  | $ | 110,164 |
Corporate bonds |  | 88,589 |  | 89,146 |  | 81,214 |  | 82,351 |
Fixed rate municipal notes and bonds |  | 17,718 |  | 17,788 |  | 20,564 |  | 20,648 |
Emerging markets debt mutual fund |  | 17,693 |  | 16,399 |  | – |  | – |
Collateralized mortgage obligations |  | 14,915 |  | 15,011 |  | 12,329 |  | 12,380 |
U.S. Government agency securities |  | 9,720 |  | 9,757 |  | 10,142 |  | 10,184 |
U.S. Treasury securities |  | 4,848 |  | 4,905 |  | 7,139 |  | 7,148 |
Asset backed debt securities |  | 3,533 |  | 3,533 |  | 2,847 |  | 2,848 |
Enhanced cash mutual fund |  | – |  | – |  | 60,256 |  | 60,302 |
Other |  | 1,480 |  | 1,484 |  | 2,360 |  | 2,355 |
Total available-for-sale short-term investments |  | 297,916 |  | 297,443 |  | 307,015 |  | 308,380 |
High yield trading debt securities |  | 20,155 |  | 20,750 |  | 19,447 |  | 20,783 |
Emerging markets trading debt mutual funds |  | 2,620 |  | 2,487 |  | – |  | – |
Emerging markets trading debt securities |  | 2,444 |  | 2,355 |  | 1,918 |  | 2,072 |
Other trading debt securities |  | 218 |  | 221 |  | 889 |  | 970 |
Total short-term investments |  | $ | 323,353 |  | $ | 323,256 |  | $ | 329,269 |  | $ | 332,205
Summary of estimated fair value of fixed rate securities designated as available-for-sale, classified by the contractual maturity date of the security |
(Thousands of dollars) |  | 2011 |
Due within one year |  | $ | 31,349 |
Due after one year through three years |  | 60,281 |
Due after three years |  | 23,892 |
Total fixed rate securities |  | $ | 115,522

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