Customer Financing (Financing Receivable Credit Quality Indicators) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	$ 2,336	$ 2,442
B B B Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	1,118	1,201
B B Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	57	63
B Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	146	51
C C C Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	460	511
D Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	454	524
Other Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	$ 101	$ 92