Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130533-203044

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of decrease in right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time from transfer to receivable due to right to consideration becoming unconditional.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130551-203045

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

+ References

No definition available.

+ Details

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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- Definition

Amount of increase(decrease) in revenue recognized from contract terminations which increases (decreases) right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

+ References

No definition available.

+ Details

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

- Definition

Amount of increase (decrease) in revenue recognized from contract additions which increases (decreases) right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

+ References

No definition available.

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Balance Type:	debit
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Revenue Recognition - Contract Asset (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Contract Assets
Balance, beginning of period	$ 0
Change in accounting policy			$ 174
Contract additions	19
Terminated contracts	(1)
Reclassified to receivables	(34)
Balance, end of period	$ 10
Difference between Revenue Guidance in Effect before and after Topic 606
Contract Assets
Change in accounting policy		$ 26