Leases - Maturities of Expected Lease Revenues (Details) $ in Millions	Mar. 31, 2019 USD ($)
Leases [Abstract]
Remainder of 2019	$ 39
2020	49
2021	37
2022	24
2023	12
Thereafter	3
Total future lease maturities	$ 164

No definition available.

Total expected lease revenues.

No definition available.

Amount of lease revenues due in remainder of fiscal year following latest fiscal year.

No definition available.

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Namespace Prefix:	usm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of lease revenues due after fifth fiscal year following latest fiscal year.

No definition available.

Name:	usm_LeaseRevenuesThereafter
Namespace Prefix:	usm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of lease revenues due in fifth fiscal year following latest fiscal year.

No definition available.

Amount of lease revenues due in fourth fiscal year following latest fiscal year.

No definition available.

Amount of lease revenues due in third fiscal year following latest fiscal year.

No definition available.

Name:	usm_LeaseRevenuesYearThree
Namespace Prefix:	usm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of lease revenues due in second fiscal year following the latest fiscal year.

No definition available.