Cover - USD ($)	12 Months Ended
	Dec. 31, 2020	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-35134
Entity Registrant Name	LEVEL 3 PARENT, LLC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-0210602
Entity Address, Address Line One	1025 Eldorado Blvd.,
Entity Address, City or Town	Broomfield,
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80021-8869
City Area Code	720
Local Phone Number	888-1000
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	0
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE: None.
Entity Public Float		$ 0
Entity Central Index Key	0000794323
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY