Customer Financing (Financing Receivable Credit Quality Indicators) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	$ 1,905	$ 2,286
BBB Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage Of Credit Default Rates Applied To Customers	2.00%
Total financing receivables	1,055	1,091
BB Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables		58
B Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage Of Credit Default Rates Applied To Customers	16.00%
Total financing receivables	633	585
CCC Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	131	457
Other Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	$ 86	$ 95