CONSOLIDATED STATEMENTS OF STOCKHOLDER'S EQUITY (parenthetical) $ in Millions	Jan. 01, 2020 USD ($)
RETAINED EARNINGS (ACCUMULATED DEFICIT)
Cumulative effect of new accounting principle in period of adoption, tax	$ 1

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