Debt (Schedule of Short-term Debt) (Details) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Short-Term Borrowings and Current Installments of Long-Term Debt - Third Party and Affiliates
Current installments of long-term debt		$ 62	$ 63
Short-term borrowings, including amounts due to affiliates	[1]	89	86
Total		$ 425	$ 326
Weighted average interest rate, short-term borrowings		2.80%	2.80%
Revolving Credit Facility [Member]
Short-Term Borrowings and Current Installments of Long-Term Debt - Third Party and Affiliates
Weighted average interest rate, short-term borrowings		3.30%	4.10%
Accounts Receivable Securitization Facility [Member]
Short-Term Borrowings and Current Installments of Long-Term Debt - Third Party and Affiliates
Borrowings outstanding	[2]	$ 77	$ 80
Weighted average interest rate, short-term borrowings		2.40%	2.10%
Secured Debt [Member] | Accounts Receivable Securitization Facility [Member]
Short-Term Borrowings and Current Installments of Long-Term Debt - Third Party and Affiliates
Borrowings outstanding	[3]	$ 77
Revolving Credit Facility [Member]
Short-Term Borrowings and Current Installments of Long-Term Debt - Third Party and Affiliates
Borrowings outstanding	[2]	197	$ 97
Revolving Credit Facility [Member] | Senior Unsecured Revolving Credit Facility [Member]
Short-Term Borrowings and Current Installments of Long-Term Debt - Third Party and Affiliates
Borrowings outstanding	[4]	$ 197

[1] The weighted average interest rate was 2.8% and 2.8% as of March 31, 2018 and December 31, 2017, respectively.

[2] The weighted average interest rate was 2.4% and 2.1% as of March 31, 2018 and December 31, 2017, respectively.

[3] The Company borrowed $25 million and repaid $28 million during the three months ended March 31, 2018.

[4] The Company borrowed $435 million and repaid $335 million under its senior unsecured revolving credit facility during the three months ended March 31, 2018.