Customer Financing (Allowance For Losses On Financing Receivables) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance - January 1	$ (70)	$ (353)	$ (302)
Customer financing valuation benefit/(provision)	10	269	(51)
Reduction in customer financing assets		14
Ending balance - December 31	(60)	(70)	(353)
Collectively evaluated for impairment	$ (60)	$ (70)	$ (353)