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Revenue Recognition - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Revenue from Contract with Customer [Abstract] |  |  |
Amounts recorded gross in revenues that are billed to customers and remitted to governmental authorities | $ 56 | $ 53 | $ 67
Capitalized contract cost |  |  |
Contract cost assets | 124 | 133 |
Amortization of contract cost assets | $ 104 | $ 109 | $ 108

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- Definition Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054 + Details
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Period Type: | duration

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- Definition Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054 + Details
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- References No definition available. + Details
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- References No definition available. + Details
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- Definition The total Universal Service Funds and other surcharges recorded gross in revenues that are billed to customers and remitted to governmental authorities. + References No definition available. + Details
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Namespace Prefix: | usm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration