Basis of Presentation and Summary of Significant Accounting Policies (Details 4) shares in Millions	Dec. 31, 2017 $ / shares shares
Common Stock
Class of Stock [Line Items]
Unissued shares of CenturyLink common stock	4
Common Stock \| Stock compensation plan
Class of Stock [Line Items]
Unissued shares of CenturyLink common stock	45
Preferred Stock
Class of Stock [Line Items]
Preferential preferred stock distribution (in dollars per share) \| $ / shares	$ 25

The price per share at which the preferred stock of an entity that has priority over common stock in the distribution of dividends and in the event of liquidation of the entity is redeemed or may be called at. The redemption features of this preferred stock are solely within the control of the issuer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21475-112644

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21564-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21488-112644

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant