Segment Information - Segment Results and Operating Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Operating revenues by products and services
Revenue	$ 4,390	$ 4,887	$ 13,678	$ 14,840
Cost of services and products	1,999	2,151	6,042	6,402
Selling, general and administrative	792	654	2,407	2,172
Gain on sale of business	(593)		(593)	0
Less: stock-based compensation	(23)	(27)	(71)	(89)
Total expense	2,175	2,778	7,785	8,485
Total adjusted EBITDA	2,215	2,109	5,893	6,355
Operating Segments
Operating revenues by products and services
Revenue	4,390	4,887	13,678	14,840
Cost of services and products	817	903	2,543	2,733
Selling, general and administrative	432	421	1,284	1,307
Gain on sale of business	0		0
Less: stock-based compensation	0	0	0	0
Total expense	1,249	1,324	3,827	4,040
Total adjusted EBITDA	3,141	3,563	9,851	10,800
Operating Segments | Business
Operating revenues by products and services
Revenue	3,217	3,508	10,034	10,625
Cost of services and products	792	867	2,452	2,614
Selling, general and administrative	263	293	845	892
Gain on sale of business	0		0
Less: stock-based compensation	0	0	0	0
Total expense	1,055	1,160	3,297	3,506
Total adjusted EBITDA	2,162	2,348	6,737	7,119
Operating Segments | Mass Markets
Operating revenues by products and services
Revenue	1,173	1,379	3,644	4,215
Cost of services and products	25	36	91	119
Selling, general and administrative	169	128	439	415
Gain on sale of business	0		0
Less: stock-based compensation	0	0	0	0
Total expense	194	164	530	534
Total adjusted EBITDA	979	1,215	3,114	3,681
Segment Reconciling Items
Operating revenues by products and services
Revenue	0	0	0	0
Cost of services and products	1,182	1,248	3,499	3,669
Selling, general and administrative	360	233	1,123	865
Gain on sale of business	(593)		(593)
Less: stock-based compensation	(23)	(27)	(71)	(89)
Total expense	926	1,454	3,958	4,445
Total adjusted EBITDA	$ (926)	$ (1,454)	$ (3,958)	$ (4,445)