Customer Financing (Financing Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	$ 2,199	$ 2,386
BBB Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	1,130	1,170
BB Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	490	627
B Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	173	177
CCC Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	$ 406	$ 412