Debt (Schedule of Short-term Debt) (Details) - USD ($) $ in Millions		Jun. 30, 2018	Dec. 31, 2017
Short-Term Borrowings and Current Installments of Long-Term Debt - Third Party and Affiliates
Current installments of long-term debt		$ 68	$ 63
Short-term borrowings, including amounts due to affiliates	[1]	96	86
Total		$ 366	$ 326
Weighted average interest rate, short-term borrowings		3.50%	3.40%
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		3.50%	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		2.80%	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]	125	$ 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]	$ 125

[1] The weighted average interest rate was 3.5% and 3.4% as of June 30, 2018 and December 31, 2017, respectively.

[2] The weighted average interest rate was 2.8% and 2.1% as of June 30, 2018 and December 31, 2017, respectively.

[3] The Company borrowed $25 million and repaid $28 million during the six months ended June 30, 2018.

[4] The Company borrowed $535 million and repaid $507 million under its senior unsecured revolving credit facility during the six months ended June 30, 2018.