v3.8.0.1

Investments (Tables) | 9 Months Ended
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Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract] |
Components of Investments | Investments consisted of the following as of September 30, 2017:
|  | Cost Basis |  | Unrealized Gains |  | Unrealized Losses |  | Fair Value
|  | (Thousands of dollars)
Investments: |  |  |  |  |  |  |  |
Money market mutual funds |  | $ | 5,278 |  |  | $ | — |  |  | $ | — |  |  | $ | 5,278 |
Commercial paper |  | 9,423 |  |  | — |  |  | (10 | ) |  | 9,413 |
U.S. Government agencies |  | 13,505 |  |  | — |  |  | (14 | ) |  | 13,491 |
Corporate bonds and notes |  | 188,515 |  |  | 3 |  |  | (283 | ) |  | 188,235 |
Subtotal |  | 216,721 |  |  | 3 |  |  | (307 | ) |  | 216,417 |
Deferred compensation plan assets included in other assets |  | 2,630 |  |  | — |  |  | — |  |  | 2,630 |
Total |  | $ | 219,351 |  |  | $ | 3 |  |  | $ | (307 | ) |  | $ | 219,047 |
Investments consisted of the following as of December 31, 2016:
|  | Cost Basis |  | Unrealized Gains |  | Unrealized Losses |  | Fair 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:
|  | September 30, 2017 |  | December 31, 2016
|  | Amortized Costs |  | Fair Value |  | Amortized Costs |  | Fair Value
|  | (Thousands of dollars)
Due in one year or less |  | $ | 133,633 |  |  | $ | 133,481 |  |  | $ | 184,587 |  |  | $ | 184,334 |
Due within two years |  | 77,810 |  |  | 77,658 |  |  | 100,816 |  |  | 100,378 |
Total |  | $ | 211,443 |  |  | $ | 211,139 |  |  | $ | 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:
|  | September 30, 2017 |  | December 31, 2016
|  | Average Coupon Rate (%) |  | Average Days To Maturity |  | Average Coupon Rate (%) |  | Average Days To Maturity
Commercial paper |  | 1.236 |  |  | 228 |  | 1.001 |  |  | 184
U.S. Government agencies |  | 1.213 |  |  | 325 |  | 0.970 |  |  | 400
Corporate bonds and notes |  | 1.715 |  |  | 295 |  | 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:
|  | September 30, 2017 |  | December 31, 2016
|  | Fair Value |  | Unrealized Losses |  | Fair Value |  | Unrealized Losses
|  | (Thousands of dollars)
Commercial paper |  | $ | 9,413 |  |  | $ | (10 | ) |  | $ | 27,867 |  |  | $ | (39 | )
U.S. Government agencies |  | 9,495 |  |  | (10 | ) |  | 13,263 |  |  | (32 | )
Corporate bonds and notes |  | 102,767 |  |  | (173 | ) |  | 210,836 |  |  | (602 | )
Total |  | $ | 121,675 |  |  | $ | (193 | ) |  | $ | 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:
|  | September 30, 2017 |  | December 31, 2016
|  | Fair Value |  | Unrealized Losses |  | Fair Value |  | Unrealized Losses
|  | (Thousands of dollars)
U.S. Government agencies |  | $ | 3,996 |  |  | $ | (4 | ) |  | $ | — |  |  | $ | — |
Corporate bonds and notes |  | 77,187 |  |  | (110 | ) |  | 24,196 |  |  | (20 | )
Total |  | $ | 81,183 |  |  | $ | (114 | ) |  | $ | 24,196 |  |  | $ | (20 | )

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