Investments (Tables)
|
9 Months Ended |
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 | ) |
|