Acquisition of Level 3 - Aggregate Consideration (Details) - USD ($) $ in Millions		10 Months Ended	12 Months Ended
	Nov. 01, 2017	Oct. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill			$ 21,534	$ 28,031	$ 30,475
Purchase Price Adjustments
Acquired finite-lived intangible assets, weighted average useful life			8 years
Customer relationships
Purchase Price Adjustments
Acquired finite-lived intangible assets, weighted average useful life			9 years
Level 3 Parent, LLC
Business Acquisition [Line Items]
Cash, accounts receivable and other current assets		$ 3,291			3,317
Property, plant and equipment		9,468			9,311
Other noncurrent assets		998			782
Current liabilities, excluding current maturities of long-term debt		(1,493)			(1,461)
Current maturities of long-term debt		(7)			(7)
Long-term debt	$ (10,600)	(10,888)			(10,888)
Deferred revenue and other liabilities		(1,743)			(1,629)
Goodwill		11,177			10,837
Total estimated aggregate consideration		19,612			19,617
Purchase Price Adjustments
Cash, accounts receivable and other current assets		(26)
Property, plant and equipment		157
Other noncurrent assets		216
Current liabilities, excluding current maturities of long-term debt		(32)
Current maturities of long-term debt		0
Long-term debt		0
Deferred revenue and other liabilities		(114)
Goodwill		340
Total estimated aggregate consideration		(5)
Accounts receivable, contractual value	$ 884	884
Acquired finite-lived intangible assets, weighted average useful life	12 years
Level 3 Parent, LLC | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets		8,431			8,964
Purchase Price Adjustments
Identifiable intangible assets		(533)
Level 3 Parent, LLC | Other intangible assets
Business Acquisition [Line Items]
Identifiable intangible assets		378			$ 391
Purchase Price Adjustments
Identifiable intangible assets		$ (13)