CenturyLink Merger - Preliminary Estimated Aggregate Consideration (Details) - USD ($) $ in Millions		3 Months Ended
	Nov. 01, 2017	Mar. 31, 2018	Dec. 31, 2017
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill		$ 11,141	$ 10,837
Purchase Price Adjustments
Acquired finite-lived intangible assets weighted average remaining useful lives		11 years 7 months 6 days
CenturyLink | Level 3 Parent, LLC
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Cash, accounts receivable and other current assets		$ 3,314	3,317
Property, plant and equipment		9,403	9,311
Other noncurrent assets		938	782
Current liabilities, excluding current maturities of long-term debt		(1,461)	(1,461)
Current maturities of long-term debt		(7)	(7)
Long-term debt	$ (10,600)	(10,888)	(10,888)
Deferred revenue and other liabilities		(1,678)	(1,613)
Goodwill	11,141	11,141	10,837
Total estimated aggregate consideration		19,628	19,633
Purchase Price Adjustments
Cash, accounts receivable and other current assets		(3)
Property, plant and equipment		92
Other noncurrent assets		156
Current liabilities, excluding current maturities of long-term debt		0
Current maturities of long-term debt		0
Long-term debt		0
Deferred revenue and other liabilities		(65)
Goodwill		304
Total estimated aggregate consideration		(5)
Accounts receivable	863
Accounts receivable contractual value	884
Accounts receivable, uncollectible	$ 21
Acquired finite-lived intangible assets weighted average remaining useful lives	12 years
CenturyLink | Customer Relationships | Level 3 Parent, LLC
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Identifiable intangible assets		8,488	8,964
Purchase Price Adjustments
Identifiable intangible assets		(476)
CenturyLink | Other Intangible Assets | Level 3 Parent, LLC
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Identifiable intangible assets		378	$ 391
Purchase Price Adjustments
Identifiable intangible assets		$ (13)