Goodwill, Customer Relationships and Other Intangible Assets - Goodwill Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill Activity
Goodwill at the beginning of the period	$ 30,475	$ 19,650
Goodwill acquired during period	282	10,825
Goodwill impairment	(2,726)	0	$ 0
Goodwill at the end of the period	28,031	30,475	19,650
Foreign currency translation gain (loss)	(58)
Level 3 Parent, LLC
Goodwill Activity
Goodwill at the beginning of the period	10,837
Goodwill at the end of the period		10,837
Business
Goodwill Activity
Goodwill at the beginning of the period	20,197	9,372
Goodwill acquired during period	250	10,825
Goodwill impairment	0
Goodwill at the end of the period	20,447	20,197	9,372
Goodwill accumulated impairment loss	1,100
Consumer
Goodwill Activity
Goodwill at the beginning of the period	10,278	10,278
Goodwill acquired during period	32	0
Goodwill impairment	(2,726)
Goodwill at the end of the period	7,584	$ 10,278	$ 10,278
Consumer | Level 3 Parent, LLC
Goodwill Activity
Goodwill acquired during period	$ 32