Debt (Schedule of Balances Available for Borrowings)(Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowings outstanding	$ 0
Letters of credit issued	0
Available for borrowing	600
Credit-Linked Revolving Facility [Member]
Debt Instrument [Line Items]
Borrowings outstanding	0	50
Letters of credit issued	80
Available for borrowing	1
Accounts Receivable Securitization Facility [Member]
Debt Instrument [Line Items]
Borrowings outstanding	100
Letters of credit issued	0
Available for borrowing	$ 31