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v3.21.1

Lease Accounting (Narrative) (Details) | 3 Months Ended
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Mar. 31, 2021 contract superfundSites
Lessee, Lease, Description [Line Items] |
Number of leases with restrictive covenants | superfundSites | 102
Minimum |
Lessee, Lease, Description [Line Items] |
Remaining lease term | 1 year
Lease renewal term | 5 years
Maximum |
Lessee, Lease, Description [Line Items] |
Remaining lease term | 35 years
Lease renewal term | 20 years
Land |
Lessee, Lease, Description [Line Items] |
Number of leases | 392
Terminal |
Lessee, Lease, Description [Line Items] |
Number of leases | 1
Office Building |
Lessee, Lease, Description [Line Items] |
Number of leases | 1
Hangar |
Lessee, Lease, Description [Line Items] |
Number of leases | 1

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- Definition Lease, Remaining Lease Term + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

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- Definition Lessee, Lease, Renewal Term + References No definition available. + Details
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Namespace Prefix: | musa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Lessee, Operating Lease, Number Of Contracts + References No definition available. + Details
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Namespace Prefix: | musa_
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Balance Type: | na
Period Type: | duration

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- Definition Lessee, Operating Lease, Number Of Contracts With Restrictive Covenants + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Balance Type: | na
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=musa_TerminalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=srt_OfficeBuildingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=musa_HangarMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |