Customer Financing (Financing Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	$ 2,041	$ 2,289
BBB Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	1,170	1,324
BB Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	627	538
B Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	177	383
CCC Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	$ 67	$ 44