Divestitures of the Latin American, ILEC and EMEA Businesses (Details)								3 Months Ended			12 Months Ended
	Oct. 31, 2023 USD ($)	Oct. 31, 2022 USD ($)	Oct. 03, 2022 USD ($) state	Aug. 01, 2022 USD ($)	Oct. 31, 2021 USD ($)	Jul. 31, 2021 USD ($)	Jan. 31, 2021 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Nov. 01, 2023 USD ($)	Jul. 25, 2021 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposal groups held for sale											$ 0	$ (40,000,000)	$ 0
Goodwill										$ 12,657,000,000	1,964,000,000	12,657,000,000	15,986,000,000
Reclassification of realized loss on foreign currency translation				$ 112,000,000							382,000,000	112,000,000	0
Goodwill impairment	$ 1,900,000,000				$ 0	$ 0	$ 0	$ 8,800,000,000			10,693,000,000	3,271,000,000	$ 0
Purchaser of ILEC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments for purchase of services									$ 89,000,000
Purchase obligation			$ 373,000,000
Purchase obligation period (in years)			3 years
Pension Plans
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Reclassified of net actuarial loss and prior service credit, net of tax			$ 403,000,000
Purchaser of ILEC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchase obligation			$ 67,000,000
Purchase obligation period (in years)			3 years
Disposal Group, Held-for-sale, Not Discontinued Operations | Latin American Business | Level 3 Parent, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration from disposal of business															$ 2,700,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations | ILEC Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration from disposal of business			$ 7,500,000,000
Long term debt, net of discounts			1,500,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations | EMEA Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill impairment		$ 43,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Latin American Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposal groups held for sale												597,000,000
Indemnifications related to the sale of businesses										86,000,000		86,000,000
Net assets				1,900,000,000
Property, plant and equipment, net accumulated depreciation				1,700,000,000
Goodwill				245,000,000
Accumulated amortization				140,000,000
Deferred income tax liabilities				$ 154,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | ILEC Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposal groups held for sale												176,000,000
Indemnifications related to the sale of businesses										89,000,000		89,000,000
Net assets			4,800,000,000
Property, plant and equipment, net accumulated depreciation			3,600,000,000
Goodwill			$ 2,600,000,000
Number of states in which the business is conducted | state			20
Consideration after closing adjustments			$ 400,000,000
Long term debt, net of discounts			1,400,000,000
Net proceeds from sales of colocation business and data centers			$ 5,600,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | EMEA Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposal groups held for sale											$ 102,000,000	$ (660,000,000)
Net assets														$ 2,100,000,000
Property, plant and equipment, net accumulated depreciation														2,000,000,000
Accumulated amortization														107,000,000
Goodwill impairment										$ 43,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | EMEA Business | Level 3 Parent, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration from disposal of business														$ 1,700,000,000