Acquisition of Level 3 - 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		$ 30,778	$ 30,475
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		(1,694)	(1,629)
Goodwill		11,141	10,837
Total estimated aggregate consideration		19,612	19,617
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]
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	866
Accounts receivable contractual value	884
Accounts receivable, uncollectible	$ 18
Weighted average useful life	12 years
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
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]
Identifiable intangible assets		(476)
Other intangible assets | Level 3 Parent, LLC
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Identifiable intangible assets		378	$ 391
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]
Identifiable intangible assets		$ (13)