Segment Information - Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Total segment adjusted EBITDA	$ 2,085	$ 2,215		$ 4,294	$ 4,443
Depreciation and amortization	(1,162)	(1,196)		(2,322)	(2,384)
Impairment of goodwill	0	0	$ (6,500)	0	(6,506)
Stock-based compensation	(20)	(43)		(89)	(76)
Total other expense, net	(390)	(474)		(937)	(1,002)
INCOME (LOSS) BEFORE INCOME TAXES	513	502		946	(5,525)
Income tax expense	136	131		255	269
NET INCOME (LOSS)	377	371		691	(5,794)
Operating segments
Segment Reporting Information [Line Items]
Total segment adjusted EBITDA	3,784	3,941		7,612	7,915
Operations and Other
Segment Reporting Information [Line Items]
Total segment adjusted EBITDA	(1,699)	(1,726)		(3,318)	(3,472)
Depreciation and amortization	(1,162)	(1,196)		(2,322)	(2,384)
Impairment of goodwill	0	0		0	(6,506)
Other operating expenses	(1,699)	(1,726)		(3,318)	(3,472)
Operating income (loss)	903	976		1,883	(4,523)
Total other expense, net	$ (390)	$ (474)		$ (937)	$ (1,002)