Segment Information - Segment Results and Operating Revenue (Details ) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Operating revenues by products and services
Revenues	$ 13,108	$ 14,557	$ 17,478
Cost of services and products	6,703	7,144	7,868
Business
Operating revenues by products and services
Revenues	10,363	11,583	13,099
Cost of services and products	3,063	3,248	3,436
Headcount costs	1,237	1,473	1,584
Non-headcount costs	652	807	879
Total expense	4,952	5,528	5,899
Total segment adjusted EBITDA	5,411	6,055	7,200
Mass Markets
Operating revenues by products and services
Revenues	2,745	2,974	4,379
Cost of services and products	69	79	121
Headcount costs	651	768	945
Non-headcount costs	572	610	703
Total expense	1,292	1,457	1,769
Total segment adjusted EBITDA	$ 1,453	$ 1,517	$ 2,610