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EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Notes) | 3 Months Ended
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Mar. 31, 2021
Defined Benefit Plan [Abstract] |
EMPLOYEE BENEFIT PLANS | EMPLOYEE BENEFIT PLANS The following table sets forth the components of net periodic benefit cost for our retirement and other postretirement benefit plans for the periods indicated:
| Retirement Benefits |  | Other Postretirement Benefits
| Three Months Ended |  | Three Months Ended
| March 31, |  | March 31,
| 2021 |  | 2020 |  | 2021 |  | 2020
| (Thousands of dollars)
Components of net periodic benefit cost (income) |  |  |  |  |  |  |
Service cost | $ | 2,076 |  |  | $ | 2,036 |  |  | $ | 115 |  |  | $ | 115 |
Interest cost | 4,220 |  |  | 4,574 |  |  | 442 |  |  | 442 |
Expected return on plan assets | (6,269) |  |  | (6,232) |  |  | (722) |  |  | (722) |
Amortization of prior service cost (a) | 28 |  |  | 28 |  |  | — |  |  | — |
Amortization of net loss (a) | 4,913 |  |  | 4,571 |  |  | 1 |  |  | 1 |
Net periodic benefit cost (income) | $ | 4,968 |  |  | $ | 4,977 |  |  | $ | (164) |  |  | $ | (164) |
(a) - These components of net periodic benefit cost (income) are recognized in accumulated other comprehensive loss and are reclassified to other expense in our Consolidated Statements of Income, with related income tax benefits of $1.1 million reclassified to income tax (expense) benefit for both the three months ended March 31, 2021 and 2020.

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- References No definition available. + Details
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- Definition The entire disclosure for pension and other postretirement benefits. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -URI http://asc.fasb.org/topic&trid=2235017 + Details
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