Debt (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Short-term debt [Abstract]
Current portion of long-term debt		$ 2
Other - short-term	$ 32	44
Short-term debt	32	46
Long-term debt
Long-term debt	$ 348	347
Line of Credit Facility, Interest Rate Description	0.0175
Amended LOC Agreement Facility Capacity	$ 5
LOC Collateral Percentage for draws in the U.S. dollars	103.00%
Letters of Credit Outstanding, Amount	$ 2
Debt Instrument, Collateral	1
LOC Facility issued by local affiliates [Member]
Long-term debt
Letters of Credit Outstanding, Amount	$ 14
Revolving Credit Facility [Member]
Long-term debt
Debt Instrument, face amount		300
Term Loan [Member]
Long-term debt
Unsecured long-term debt, non-current	348	$ 347
Debt Instrument, face amount	$ 350
Term loan, required periodic payment	0.0175
Affiliated Entity [Member]
Long-term debt
Line of Credit Facility, Capacity Available for Trade Purchases	$ 25
Revolving Credit Facility [Member]
Long-term debt
Line of Credit Facility, Maximum Borrowing Capacity	75
borrowing capacity under swing line advances	$ 20
Maximum [Member]
Long-term debt
Line of Credit Facility, Interest Rate Description	0.0225
Debt Instrument, Covenant Description	3
Minimum [Member]
Long-term debt
Line of Credit Facility, Interest Rate Description	0.0125
Debt Instrument, Covenant Description	1
Domestic rate [Member]
Long-term debt
Line of Credit Facility, Interest Rate Description	0.0075