Segment Information - Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Total adjusted EBITDA	$ 2,109	$ 2,112	$ 6,355	$ 6,406
Depreciation and amortization	(951)	(1,193)	(3,142)	(3,515)
OPERATING INCOME	1,131	888	3,124	2,771
Total other expense, net	(415)	(408)	(1,102)	(1,345)
INCOME BEFORE INCOME TAXES	716	480	2,022	1,426
Income tax expense	172	114	497	369
NET INCOME	544	366	1,525	1,057
Operating Segments
Segment Reporting Information [Line Items]
Total adjusted EBITDA	3,562	3,753	10,803	11,290
Operations and Other
Segment Reporting Information [Line Items]
Total adjusted EBITDA	(1,453)	(1,641)	(4,448)	(4,884)
Depreciation and amortization	(951)	(1,193)	(3,142)	(3,515)
Other operating expenses	(1,453)	(1,641)	(4,448)	(4,884)
Stock-based compensation	(27)	(31)	(89)	(120)
OPERATING INCOME	1,131	888	3,124	2,771
Total other expense, net	$ (415)	$ (408)	$ (1,102)	$ (1,345)