XML 78 R67.htm IDEA: XBRL DOCUMENT
v3.23.3

Assets and Liabilities Measured at Fair Value (Schedule of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Financial assets |  |
Marketable securities, current | $ 8.5 | $ 17.9
U.S. Corporate bonds | 7.4 | 4.4
Fair Value, Recurring |  |
Financial assets |  |
Derivatives |  | 1.3
Financial liabilities |  |
Fair value, net asset (liability) | 8.9 | 18.4
Fair Value, Recurring | Fuel derivative |  |
Financial assets |  |
Derivatives | 0.2 |
Fair Value, Recurring | Deferred compensation plan liabilities |  |
Financial liabilities |  |
Deferred compensation plan liabilities | (18.7) | (14.7)
Fair Value, Recurring | Deferred compensation plan assets |  |
Financial assets |  |
Deferred compensation plan assets | 11.5 | 9.5
Fair Value, Recurring | U.S. Government bonds |  |
Financial assets |  |
Marketable securities, current | 5.9 | 8.8
Fair Value, Recurring | U.S. Corporate bonds |  |
Financial assets |  |
Marketable securities, current | 2.6 | 6.1
U.S. Corporate bonds | 5.9 | 4.4
Fair Value, Recurring | Non U.S. Corporate bonds |  |
Financial assets |  |
Marketable securities, current |  | 3.0
U.S. Corporate bonds | 1.5 |
Fair Value, Recurring | Level 1 |  |
Financial assets |  |
Derivatives |  | 0.0
Financial liabilities |  |
Fair value, net asset (liability) | (7.2) | (5.2)
Fair Value, Recurring | Level 1 | Fuel derivative |  |
Financial assets |  |
Derivatives | 0.0 |
Fair Value, Recurring | Level 1 | Deferred compensation plan liabilities |  |
Financial liabilities |  |
Deferred compensation plan liabilities | (18.7) | (14.7)
Fair Value, Recurring | Level 1 | Deferred compensation plan assets |  |
Financial assets |  |
Deferred compensation plan assets | 11.5 | 9.5
Fair Value, Recurring | Level 1 | U.S. Government bonds |  |
Financial assets |  |
Marketable securities, current | 0.0 | 0.0
Fair Value, Recurring | Level 1 | U.S. Corporate bonds |  |
Financial assets |  |
Marketable securities, current | 0.0 | 0.0
U.S. Corporate bonds | 0.0 | 0.0
Fair Value, Recurring | Level 1 | Non U.S. Corporate bonds |  |
Financial assets |  |
Marketable securities, current |  | 0.0
U.S. Corporate bonds | 0.0 |
Fair Value, Recurring | Level 2 |  |
Financial assets |  |
Derivatives |  | 0.0
Financial liabilities |  |
Fair value, net asset (liability) | 15.9 | 22.3
Fair Value, Recurring | Level 2 | Fuel derivative |  |
Financial assets |  |
Derivatives | 0.0 |
Fair Value, Recurring | Level 2 | Deferred compensation plan liabilities |  |
Financial liabilities |  |
Deferred compensation plan liabilities | 0.0 | 0.0
Fair Value, Recurring | Level 2 | Deferred compensation plan assets |  |
Financial assets |  |
Deferred compensation plan assets | 0.0 | 0.0
Fair Value, Recurring | Level 2 | U.S. Government bonds |  |
Financial assets |  |
Marketable securities, current | 5.9 | 8.8
Fair Value, Recurring | Level 2 | U.S. Corporate bonds |  |
Financial assets |  |
Marketable securities, current | 2.6 | 6.1
U.S. Corporate bonds | 5.9 | 4.4
Fair Value, Recurring | Level 2 | Non U.S. Corporate bonds |  |
Financial assets |  |
Marketable securities, current |  | 3.0
U.S. Corporate bonds | 1.5 |
Fair Value, Recurring | Level 3 |  |
Financial assets |  |
Derivatives |  | 1.3
Financial liabilities |  |
Fair value, net asset (liability) | 0.2 | 1.3
Fair Value, Recurring | Level 3 | Fuel derivative |  |
Financial assets |  |
Derivatives | 0.2 |
Fair Value, Recurring | Level 3 | Deferred compensation plan liabilities |  |
Financial liabilities |  |
Deferred compensation plan liabilities | 0.0 | 0.0
Fair Value, Recurring | Level 3 | Deferred compensation plan assets |  |
Financial assets |  |
Deferred compensation plan assets | 0.0 | 0.0
Fair Value, Recurring | Level 3 | U.S. Government bonds |  |
Financial assets |  |
Marketable securities, current | 0.0 | 0.0
Fair Value, Recurring | Level 3 | U.S. Corporate bonds |  |
Financial assets |  |
Marketable securities, current | 0.0 | 0.0
U.S. Corporate bonds | 0.0 | 0.0
Fair Value, Recurring | Level 3 | Non U.S. Corporate bonds |  |
Financial assets |  |
Marketable securities, current |  | $ 0.0
U.S. Corporate bonds | $ 0.0 |

X
- Definition Deferred Compensation Plan Assets, Fair Value Disclosure + References No definition available. + Details
Name: | musa_DeferredCompensationPlanAssetsFairValueDisclosure
Namespace Prefix: | musa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Deferred Compensation Plan Liabilities, Fair Value Disclosure + References No definition available. + Details
Name: | musa_DeferredCompensationPlanLiabilitiesFairValueDisclosure
Namespace Prefix: | musa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_AssetsFairValueDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481830/320-10-45-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479130/326-30-45-1 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as noncurrent. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481830/320-10-45-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(12)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479130/326-30-45-1 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483466/210-20-50-3 + Details
Name: | us-gaap_DerivativeAssetsCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of asset after deduction of liability. + References No definition available. + Details
Name: | us-gaap_FairValueNetAssetLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_LiabilitiesFairValueDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CommodityContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByLiabilityClassAxis=musa_DeferredCompensationPlanLiablitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=musa_DeferredCompensationPlanAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CorporateBondSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |