Debt (Capital Lease Obligations) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Minimum Lease Payments, Sale Leaseback Transactions, Fiscal Year Maturity [Abstract]
Minimum Lease Payments, Sale Leaseback Transactions, within One Year	$ 37	[1]
Minimum Lease Payments, Sale Leaseback Transactions, within Two Years	25	[1]
Minimum Lease Payments, Sale Leaseback Transactions, within Three Years	25	[1]
Minimum Lease Payments, Sale Leaseback Transactions, within Four Years	25	[1]
Minimum Lease Payments, Sale Leaseback Transactions, within Five Years	17	[1]
Minimum Lease Payments, Sale Leaseback Transactions, Thereafter	127	[1]
Minimum Lease Payments, Sale Leaseback Transactions	256	[1]
Interest Portion of Minimum Lease Payments, Sale Leaseback Transactions	96	[1]
Present Value of Future Minimum Lease Payments, Sale Leaseback Transactions	160	[1]
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Capital Leases, Future Minimum Payments Due, Current	42
Capital Leases, Future Minimum Payments Due in Two Years	43
Capital Leases, Future Minimum Payments Due in Three Years	38
Capital Leases, Future Minimum Payments Due in Four Years	41
Capital Leases, Future Minimum Payments Due in Five Years	38
Capital Leases, Future Minimum Payments Due Thereafter	161
Capital Leases, Future Minimum Payments Due	363
Capital Leases, Future Minimum Payments, Interest Included in Payments	146
Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments	217
Total Leases Future Minimum Payments [Abstract]
Total Leases, Future Minimum Payments Due, Current	79
Total Leases, Future Minimum Payments Due in Two Years	68
Total Leases, Future Minimum Payments Due in Three Years	63
Total Leases, Future Minimum Payments Due in Four Years	66
Total Leases, Future Minimum Payments Due in Five Years	55
Total Leases, Future Minimum Payments Due Thereafter	288
Total Leases, Future Minimum Payments Due	619
Total Leases, Future Minimum Payments, Interest Included in Payments	242
Total Leases, Future Minimum Payments, Present Value of Net Minimum Payments	$ 377

[1] Amounts are accounted for as financing transactions under U.S. GAAP and are included in our project financing, notes payable and other amounts above.