Customer Financing (Credit Risk Profile By Internally Assigned Ratings) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Accounts, Notes, Loans and Financing Receivables [Line Items]
Total carrying value of financing receivables	$ 2,851	$ 2,752
BBB Credit Rating [Member]
Accounts, Notes, Loans and Financing Receivables [Line Items]
Total carrying value of financing receivables	1,316
BB Credit Rating [Member]
Accounts, Notes, Loans and Financing Receivables [Line Items]
Total carrying value of financing receivables	67
B Credit Rating [Member]
Accounts, Notes, Loans and Financing Receivables [Line Items]
Total carrying value of financing receivables	103	207
CCC Credit Rating [Member]
Accounts, Notes, Loans and Financing Receivables [Line Items]
Total carrying value of financing receivables	512	2,432
D Credit Rating [Member]
Accounts, Notes, Loans and Financing Receivables [Line Items]
Total carrying value of financing receivables	653
Other Credit Rating [Member]
Accounts, Notes, Loans and Financing Receivables [Line Items]
Total carrying value of financing receivables	$ 200	$ 113