Debt (Schedule of Accounts Receivable Securitization Facility)(Details) - Accounts Receivable Securitization Facility [Member] - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Borrowings outstanding	[1]	$ 77	$ 80
Secured Debt [Member]
Debt Instrument [Line Items]
Borrowings outstanding	[2]	77
Letters of credit issued		29
Available for borrowing		14
Total borrowing base		120
Maximum borrowing base	[3]	120
Proceeds from Issuance of Debt		25
Repayments of Lines of Credit		28
Outstanding accounts receivable transferred by the Originators to the Transferor		$ 176

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

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

[3] Outstanding accounts receivable transferred to the SPE was $176 million.