Customer Financing (Financing Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	$ 2,043	$ 2,386
BBB Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	1,023	1,170
BB Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	450	627
B Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	167	177
CCC Credit Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Carrying value of financing receivables	$ 403	$ 412