Income Taxes - Narrative (Details) € in Millions, $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2018 EUR (€)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017	Dec. 31, 2017 USD ($)
Income Tax Disclosure [Abstract]
Effective income tax rate reconciliation, percent				26.50%	28.50%
Effective income tax rate reconciliation, including discrete items, percent	35.30%	35.30%	30.80%
Discrete income tax expense	$ 26		$ 2
Prior year adjustments	13
Reversal of a foreign tax reserve that is effectively settled	38
Tax Cuts And Jobs Act of 2017, incomplete accounting, provisional income tax expense (benefit)	(8)			$ 13		$ 272
Tax Cuts and Jobs Act of 2017, incomplete accounting, transition tax benefit	2
Tax Cuts and Jobs Act of 2017, incomplete accounting, change in tax rate benefit	6
Increase in estimate of one-time transition tax				16
Charges recorded for alternative minimum tax credits				(3)
U.S. tax rate change impacts				$ 6
Spain
Operating Loss Carryforwards [Line Items]
Established tax reserve	$ 59	€ 51