v3.7.0.1

Investments (Tables) | 3 Months Ended
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Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract] |
Components of Investments | Investments consisted of the following as of March 31, 2017:
|  |  |  |  | Unrealized |  |  | Unrealized |  |  | Fair |
|  | Cost Basis |  |  | Gains |  |  | Losses |  |  | Value |
|  | (Thousands of dollars) |
Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market mutual funds |  | $ | 10,597 |  |  | $ | — |  |  | $ | — |  |  | $ | 10,597 |
Commercial paper |  |  | 27,935 |  |  |  | — |  |  |  | (26 | ) |  |  | 27,909 |
U.S. Government agencies |  |  | 15,305 |  |  |  | — |  |  |  | (20 | ) |  |  | 15,285 |
Corporate bonds and notes |  |  | 236,525 |  |  |  | 4 |  |  |  | (479 | ) |  |  | 236,050 |
Subtotal |  |  | 290,362 |  |  |  | 4 |  |  |  | (525 | ) |  |  | 289,841 |
Deferred compensation plan assets included in other assets |  |  | 2,500 |  |  |  | — |  |  |  | — |  |  |  | 2,500 |
Total |  | $ | 292,862 |  |  | $ | 4 |  |  | $ | (525 | ) |  | $ | 292,341 |
Investments consisted of the following as of December 31, 2016:
|  |  |  |  | Unrealized |  |  | Unrealized |  |  | Fair |
|  | Cost Basis |  |  | Gains |  |  | Losses |  |  | Value |
|  | (Thousands of dollars) |
Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market mutual funds |  | $ | 18,118 |  |  | $ | — |  |  | $ | — |  |  | $ | 18,118 |
Commercial paper |  |  | 27,906 |  |  |  | — |  |  |  | (39 | ) |  |  | 27,867 |
U.S. government agencies |  |  | 13,295 |  |  |  | — |  |  |  | (32 | ) |  |  | 13,263 |
Corporate bonds and notes |  |  | 244,202 |  |  |  | 2 |  |  |  | (622 | ) |  |  | 243,582 |
Subtotal |  |  | 303,521 |  |  |  | 2 |  |  |  | (693 | ) |  |  | 302,830 |
Deferred compensation plan assets included in other assets |  |  | 2,394 |  |  |  | — |  |  |  | — |  |  |  | 2,394 |
Total |  | $ | 305,915 |  |  | $ | 2 |  |  | $ | (693 | ) |  | $ | 305,224 |
Cost and Fair Value of Debt Investments Based on Maturities | The following table presents the cost and fair value of our debt investments based on maturities as of:
|  | March 31, 2017 |  |  | December 31, 2016 |
|  | Amortized |  |  | Fair |  |  | Amortized |  |  | Fair |
|  | Costs |  |  | Value |  |  | Costs |  |  | Value |
|  | (Thousands of dollars) |
Due in one year or less |  | $ | 200,195 |  |  | $ | 199,906 |  |  | $ | 184,587 |  |  | $ | 184,334 |
Due within two years |  |  | 79,570 |  |  |  | 79,338 |  |  |  | 100,816 |  |  |  | 100,378 |
Total |  | $ | 279,765 |  |  | $ | 279,244 |  |  | $ | 285,403 |  |  | $ | 284,712 |
Average Coupon Rate Percentage and Average Days to Maturity of Debt | The following table presents the average coupon rate percentage and the average days to maturity of our debt investments as of:
|  | March 31, 2017 |  |  | December 31, 2016 |
|  | Average |  |  | Average |  |  | Average |  |  | Average |
|  | Coupon |  |  | Days To |  |  | Coupon |  |  | Days To |
|  | Rate (%) |  |  | Maturity |  |  | Rate (%) |  |  | Maturity |
Commercial paper |  |  | 1.035 |  |  |  | 140 |  |  |  | 1.001 |  |  |  | 184 |
U.S. Government agencies |  |  | 1.056 |  |  |  | 355 |  |  |  | 0.970 |  |  |  | 400 |
Corporate bonds and notes |  |  | 1.731 |  |  |  | 287 |  |  |  | 1.745 |  |  |  | 318 |
Investments in Continuous Unrealized Loss Position for Less Than Twelve Months | The following table presents the fair value and unrealized losses related to our investments that have been in a continuous unrealized loss position for less than twelve months as of:
|  | March 31, 2017 |  |  | December 31, 2016 |
|  |  |  |  | Unrealized |  |  |  |  |  | Unrealized |
|  | Fair Value |  |  | Losses |  |  | Fair Value |  |  | Losses |
|  | (Thousands of dollars) |
Commercial paper |  | $ | 27,909 |  |  | $ | (26 | ) |  | $ | 27,867 |  |  | $ | (39 | )
U.S. Government agencies |  |  | 14,285 |  |  |  | (20 | ) |  |  | 13,263 |  |  |  | (32 | )
Corporate bonds and notes |  |  | 207,512 |  |  |  | (460 | ) |  |  | 210,836 |  |  |  | (602 | )
Total |  | $ | 249,706 |  |  | $ | (506 | ) |  | $ | 251,966 |  |  | $ | (673 | )
Investments in Continuous Unrealized Loss Position for More Than Twelve Months | The following table presents the fair value and unrealized losses related to our investments that have been in a continuous unrealized loss position for more than twelve months as of:
|  | March 31, 2017 |  |  | December 31, 2016 |
|  |  |  |  | Unrealized |  |  |  |  |  | Unrealized |
|  | Fair Value |  |  | Losses |  |  | Fair Value |  |  | Losses |
|  | (Thousands of dollars) |
Corporate bonds and notes |  | $ | 20,116 |  |  | $ | (19 | ) |  | $ | 24,196 |  |  | $ | (20 | )
Total |  | $ | 20,116 |  |  | $ | (19 | ) |  | $ | 24,196 |  |  | $ | (20 | )

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