Customer Financing (Financing Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 67
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	138
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	78
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	15
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	291
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	739
Carrying value of financing receivables	1,328	$ 1,339
CCC Credit Rating
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	7
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	31
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	240
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	176
Carrying value of financing receivables	454
B Credit Rating
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	51
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	170
Carrying value of financing receivables	221
BB Credit Rating
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	67
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	131
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	47
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	15
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	139
Carrying value of financing receivables	399
BBB Credit Rating
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	254
Carrying value of financing receivables	$ 254