CenturyLink Merger - Consideration (Details) - USD ($) $ in Millions		10 Months Ended	12 Months Ended
	Nov. 01, 2017	Oct. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2017
Business Acquisition [Line Items]
Goodwill			$ 11,119	$ 10,837	$ 10,821
CenturyLink | Level 3 Parent, LLC
Business Acquisition [Line Items]
Cash, accounts receivable and other current assets		$ 3,291		3,317
Cash, accounts receivable and other current assets, purchase price adjustments		(26)
Property, plant and equipment		9,468		9,311
Property, plant and equipment, purchase price adjustments		157
Other non-current assets		998		782
Other noncurrent assets, purchase price adjustments		216
Current liabilities, excluding the current portion of long-term debt		(1,493)		(1,461)
Current liabilities, excluding current maturities of long-term debt, purchase price adjustments		(32)
Current maturities of long-term debt		(7)		(7)
Current maturities of long-term debt, purchase price adjustments		0
Long-term debt		(10,888)		(10,888)
Long-term debt, purchase price adjustments		0
Deferred revenue and other liabilities		(1,727)		(1,613)
Deferred revenue and other liabilities, purchase price adjustments		(114)
Goodwill		11,177		10,837
Goodwill, purchase price adjustments			$ 340
Total estimated aggregate consideration		19,628		19,633
Total estimated aggregate consideration, purchase price adjustments		(5)
Accounts receivable contractual value	$ 884
Acquired finite-lived intangible assets, weighted average useful life	12 years
CenturyLink | Level 3 Parent, LLC | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets		8,431		8,964
Identifiable intangible assets, purchase price adjustments		(533)
CenturyLink | Level 3 Parent, LLC | Other
Business Acquisition [Line Items]
Identifiable intangible assets		378		$ 391
Identifiable intangible assets, purchase price adjustments		$ (13)