Segment Information - Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Total segment adjusted EBITDA	$ 2,228	$ 2,074
Depreciation and amortization	(1,188)	(1,283)
Impairment of goodwill	(6,506)	0
Total other expense, net	(528)	(514)
INCOME (LOSS) BEFORE INCOME TAX EXPENSE	(6,027)	236
Income tax expense	(138)	(121)
NET (LOSS) INCOME	(6,165)	115
Operating segments
Segment Reporting Information [Line Items]
Total segment adjusted EBITDA	4,033	4,166
Segment Reconciling Items
Segment Reporting Information [Line Items]
Total segment adjusted EBITDA	(1,805)	(2,092)
Depreciation and amortization	(1,188)	(1,283)
Impairment of goodwill	(6,506)	0
Other operating expenses	(1,805)	(2,092)
Stock-based compensation	(33)	(41)
Operating (loss) income	(5,499)	750
Total other expense, net	$ (528)	$ (514)