Segment Information - USF surcharges and transaction taxes (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting [Abstract]
USF surcharges and transaction taxes	$ 1,002	$ 952	$ 601

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