Investments in Unconsolidated Entities, Narrative (Details) $ in Millions	Mar. 31, 2018 USD ($)
Equity Securities without Readily Determinable Fair Value [Line Items]
Measurement alternative, impairment	$ 0
Measurement alternative, observable price change	$ 0

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.

No definition available.

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Namespace Prefix:	usm_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration