Commitments and Contingencies (Details)	3 Months Ended
Mar. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Number of patents allegedly infringed (minimum)	1
Unfavorable regulatory action
Loss Contingencies [Line Items]
Estimate of possible loss (per proceeding)	$ 100,000
Subsidiaries of CenturyLink, Inc. \| Interexchange carriers
Loss Contingencies [Line Items]
Number of lawsuits (approximately)	100

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.

+ Details

Name:	us-gaap_LossContingenciesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Number of another entity's patents that the entity has allegedly infringed.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

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Namespace Prefix:
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- Details

Name:	dei_LegalEntityAxis=ctq_SubsidiariesofCenturyLinkInc.Member
Namespace Prefix:
Data Type:	na
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Period Type:

- Details

Name:	us-gaap_LitigationCaseAxis=ctq_InterexchangeCarriersMember
Namespace Prefix:
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