Customer Financing (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Customer Financing [Line Items]
Financing Receivable, Individually Evaluated for Impairment	$ 414	$ 422
Impaired Financing Receivable, Recorded Investment	$ 403	$ 411
B Credit Rating [Member]
Customer Financing [Line Items]
Percentage of Credit Default Rates Applied to Customers	23.20%
BB Credit Rating [Member]
Customer Financing [Line Items]
Percentage of Credit Default Rates Applied to Customers	7.20%
BBB Credit Rating [Member]
Customer Financing [Line Items]
Percentage of Credit Default Rates Applied to Customers	0.80%