CONSOLIDATED STATEMENTS OF STOCKHOLDER'S EQUITY (Parenthetical) $ in Millions	Dec. 31, 2018 USD ($)
RETAINED EARNINGS (ACCUMULATED DEFICIT)
Cumulative net effect of adoption of ASU 2014-09, tax	$ (49)

Cumulative Effect of New Accounting Principle in Period of Adoption, Tax

No definition available.

Name:	ctl_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoptionTax
Namespace Prefix:	ctl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant