Debt Debt (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Line of Credit Facility [Line Items]
Amortization of Purchase Accounting Premium	$ 8	$ 19
Deferred Finance Costs, Net	46		31
Accretion of Discount	5
Purchase Price Premium, Unamortized	2
Acquisition Accounting Discount - Secured Debt	48
Unsecured Debt	5,238		1,500
North America [Member]
Line of Credit Facility [Line Items]
Unsecured Debt	4,000		1,500
International [Member]
Line of Credit Facility [Line Items]
Original Weighted-Average Interest Rate - Minimum	0.90%
Original Weighted-Average Interest Rate - Maximum	6.30%
Unsecured Debt	1,238
Secured Debt [Member] | North America [Member]
Line of Credit Facility [Line Items]
Original Weighted-Average Interest Rate - Minimum	0.90%	0.90%
Original Weighted-Average Interest Rate - Maximum	5.70%	13.40%
Unsecured Debt [Member] | International [Member]
Line of Credit Facility [Line Items]
Original Weighted-Average Interest Rate - Minimum	0.00%
Original Weighted-Average Interest Rate - Maximum	9.00%
2013 Senior Notes [Member] | North America [Member]
Line of Credit Facility [Line Items]
Original Weighted-Average Interest Rate - Minimum	2.75%
Original Weighted-Average Interest Rate - Maximum	4.25%
Senior Notes	2,500
Senior Notes [Member] | North America [Member]
Line of Credit Facility [Line Items]
Original Weighted-Average Interest Rate - Minimum	2.75%
Original Weighted-Average Interest Rate - Maximum	6.75%
Senior Notes [Member]
Line of Credit Facility [Line Items]
Senior Notes	4,000
Senior Notes [Member] | North America [Member]
Line of Credit Facility [Line Items]
Unsecured Debt	4,000
Senior Notes	$ 4,000		$ 1,500