Customer Financing (Financing Receivable Credit Quality Indicators) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Total Financing Receivables	$ 2,442	$ 2,851
Internally Assigned Grade [Member] | BBB Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Financing Receivables	1,201	1,316
Internally Assigned Grade [Member] | BB Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Financing Receivables	63	67
Internally Assigned Grade [Member] | B Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Financing Receivables	51	103
Internally Assigned Grade [Member] | CCC Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Financing Receivables	511	512
Internally Assigned Grade [Member] | D Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Financing Receivables	524	653
Internally Assigned Grade [Member] | Other Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Financing Receivables	$ 92	$ 200