Commitments And Contingencies - Narrative (Details) (USD $) In Millions, unless otherwise specified			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011 Collectibility of Receivables [Member] Angola Customer [Member]
Loss Contingencies [Line Items]
Letters of Credit Outstanding, Amount	$ 42	$ 38
Accounts receivable, overdue			40
Sales Returns and Allowances, Goods			(3)
Account Receivable Present Value Estimate Reclassified to Non-current Asset			$ 22