Long-Term Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2018	Oct. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Other borrowings	$ 9			$ 9
Total debt	5,959			4,900
Less: current maturities	(4)			(3)
Long-term debt	5,955			4,897
Senior notes | 2.7% senior notes due 2020
Debt Instrument [Line Items]
Long-term debt	$ 848			846
Interest rate	2.70%		2.70%
Senior notes | 4.75% senior notes due 2021
Debt Instrument [Line Items]
Long-term debt	$ 399			398
Interest rate	4.75%		4.75%
Senior notes | 3.5% senior notes due 2022
Debt Instrument [Line Items]
Long-term debt	$ 697			696
Interest rate	3.50%		3.50%
Senior notes | 3.8% senior notes due 2023
Debt Instrument [Line Items]
Long-term debt	$ 992			0
Interest rate	3.80%		3.80%
Senior notes | 3.85% senior notes due 2025
Debt Instrument [Line Items]
Long-term debt	$ 895			894
Interest rate	3.85%		3.85%
Senior notes | 4.2% senior notes due 2028
Debt Instrument [Line Items]
Long-term debt	$ 990			0
Interest rate	4.20%		4.20%
Senior notes | 4.625% senior notes due 2020
Debt Instrument [Line Items]
Long-term debt	$ 0			$ 449
Interest rate		4.625%	4.625%	4.625%
Term loan
Debt Instrument [Line Items]
Long-term debt	0			$ 540
Revolving credit facility
Debt Instrument [Line Items]
Long-term debt	$ 1,129			$ 1,068