Threshold period for determining trade accounts receivable as past due in 'PnYnMnDTnHnMnS' format

No definition available.

Name:	ctl_AccountsReceivablePastDueThresholdDaysOutstanding
Namespace Prefix:	ctl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the term of indefeasible rights of use commonly referred to as IRUs, which are the exclusive right to use a specified amount of capacity or fiber.

+ References

No definition available.

+ Details

Name:	ctl_IndefeasibleRightsOfUseTerm
Namespace Prefix:	ctl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the customer relationship period considered for recognition of revenue.

+ References

No definition available.

+ Details

Name:	ctl_RevenueRecognitionCustomerRelationshipPeriod
Namespace Prefix:	ctl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 720
-SubTopic 35
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848

+ Details

Name:	us-gaap_AdvertisingExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_DeferredRevenueArrangementTypeAxis=ctl_ActivationandInstallationChargesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Basis of Presentation and Summary of Significant Accounting Policies (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue Recognition
Term of indefeasible rights of use (in years)	20 years
Advertising Costs
Advertising expense	$ 218	$ 216	$ 210
Accounts Receivable and Allowance for Doubtful Accounts
Accounts receivable, past due threshold (in days)	30 days
Activation and installation charges \| Minimum
Revenue Recognition
Customer relationship period for revenue recognition (from eighteen months to over ten years)	3 years
Activation and installation charges \| Maximum
Revenue Recognition
Customer relationship period for revenue recognition (from eighteen months to over ten years)	7 years