Acquisition of Level 3 - Acquisition Related Expenses (Details) - Level 3 Parent, LLC - USD ($) $ in Millions	12 Months Ended	36 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Business Acquisition [Line Items]
Transaction-related expenses	$ 0	$ 2	$ 174	$ 0
Integration and transformation-related expenses	234	391	97
Total acquisition-related expenses	$ 234	$ 393	$ 271	$ 950

Amount of direct costs of the business combination including legal, accounting, other costs incurred to consummate the business acquisition, and amount of costs incurred to effect a business combination, including business integration costs, systems integration and conversion costs, and severance and other employee-related costs.

No definition available.

Name:	ctl_BusinessCombinationTransactionCostsandIntegrationRelatedCosts
Namespace Prefix:	ctl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration