Revenue Recognition - Accounts Receivable (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable
Customer and agents	$ 908	$ 775
Roaming	20	26
Other	46	$ 41
Accounts receivable from contract with customer
Accounts receivable
Customer and agents	908
Roaming	20
Other	32
Total	$ 960

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount due from parties in nontrade transactions, classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.8)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount due from contracts with customers or clients for goods or services that have been delivered or sold.

+ References

No definition available.

+ Details

Name:	usm_AccountsReceivableFromContractWithCustomer
Namespace Prefix:	usm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Receivables, Net, Current [Line Items]

+ References

No definition available.

+ Details

Name:	usm_ReceivablesNetCurrentLineItems
Namespace Prefix:	usm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount due from third party carriers for such other carriers customers usage of the Entitys network when roaming

+ References

No definition available.

+ Details

Name:	usm_ReceivablesNetCurrentRoaming
Namespace Prefix:	usm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	usm_AccountsReceivableFromContractWithCustomersAxis=usm_AccountsReceivableFromContractWithCustomerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: