Consolidated Statements of Member's Equity (Parenthetical) $ in Millions	Jan. 01, 2018 USD ($)
Member Units \| Accounting Standards Update 2014-09
Cumulative effect of new accounting, tax	$ 3

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