Guarantor and Non-Guarantor Supplemental Financial Information - Condensed Consolidating Balance Sheet Information (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Total current assets	$ 7,969		$ 5,197
Investment in subsidiaries	0		0
Intangible assets, net	1,843		1,992
Goodwill	8,104		8,120
Other assets, net	3,465		2,724
TOTAL ASSETS	21,381		18,033
Total current liabilities	10,582		8,060
Long-term debt, excluding current maturities	4,170		3,717
Other long-term liabilities	857		575
Redeemable non-controlling interests	33		30
Stockholders’ equity	5,739	$ 5,907	5,651	$ 5,927	$ 5,552	$ 6,129
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	21,381		18,033
Reportable Legal Entities | Parent
Condensed Balance Sheet Statements, Captions [Line Items]
Total current assets	431		402
Investment in subsidiaries	10,795		10,615
Intangible assets, net	0		0
Goodwill	0		0
Other assets, net	0		0
TOTAL ASSETS	11,226		11,017
Total current liabilities	1,317		1,649
Long-term debt, excluding current maturities	4,170		3,717
Other long-term liabilities	0		0
Redeemable non-controlling interests	0		0
Stockholders’ equity	5,739		5,651
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	11,226		11,017
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Balance Sheet Statements, Captions [Line Items]
Total current assets	6,685		5,261
Investment in subsidiaries	3,041		3,425
Intangible assets, net	1,438		1,520
Goodwill	6,367		6,366
Other assets, net	2,379		1,840
TOTAL ASSETS	19,910		18,412
Total current liabilities	8,537		7,396
Long-term debt, excluding current maturities	0		0
Other long-term liabilities	477		320
Redeemable non-controlling interests	33		17
Stockholders’ equity	10,863		10,679
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	19,910		18,412
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Balance Sheet Statements, Captions [Line Items]
Total current assets	2,581		2,137
Investment in subsidiaries	0		0
Intangible assets, net	405		472
Goodwill	1,737		1,754
Other assets, net	1,120		913
TOTAL ASSETS	5,843		5,276
Total current liabilities	2,456		1,618
Long-term debt, excluding current maturities	0		0
Other long-term liabilities	414		284
Redeemable non-controlling interests	0		13
Stockholders’ equity	2,973		3,361
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	5,843		5,276
Eliminations
Condensed Balance Sheet Statements, Captions [Line Items]
Total current assets	(1,728)		(2,603)
Investment in subsidiaries	(13,836)		(14,040)
Intangible assets, net	0		0
Goodwill	0		0
Other assets, net	(34)		(29)
TOTAL ASSETS	(15,598)		(16,672)
Total current liabilities	(1,728)		(2,603)
Long-term debt, excluding current maturities	0		0
Other long-term liabilities	(34)		(29)
Redeemable non-controlling interests	0		0
Stockholders’ equity	(13,836)		(14,040)
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ (15,598)		$ (16,672)