Segment Information - USF Surcharges and Transaction Taxes (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting [Abstract]
USF surcharges and transaction taxes	$ 270	$ 221	$ 750	$ 698

Amount of the universal taxes and surcharges that are reflected in the statement of income (included in both operating revenues and expenses).

No definition available.

Name:	ctl_UniversalServiceTaxesAndSurcharges
Namespace Prefix:	ctl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration