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v3.20.2

Basis of Presentation - Narrative (Details) | Sep. 30, 2020
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TDS | UScellular |
Basis of Presentation [Line Items] |
Ownership percentage | 82.00%

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- Definition The parent entity's interest in net assets of the subsidiary, expressed as a percentage. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Used to group disclosures related to significant accounting policies. + References No definition available. + Details
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Namespace Prefix: | usm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | dei_LegalEntityAxis=usm_TelephoneandDataSystemsInc.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_OwnershipAxis=usm_UnitedStatesCellularCorporationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |