| **Allowance for Doubtful Accounts - Retail, Wholesale, Trade & Other (Details) (USD $)In Millions, unless otherwise specified** | 3 Months Ended | 6 Months Ended |
|-------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Financing Receivable, Allowance for Credit Losses [Line Items]**                                                                  |           |           |   |   |
| Number of Portfolio Segments for Finance Receivables                                                                                | 2              |           | 2 |   |
| Classes of Receivables in Each Portfolio                                                                                            | 1              |           | 1 |   |
| Allowance for doubtful accounts at beginning of period                                                                              | $ 60           | $ 49           | $ 60 | $ 51 |
| Provision for doubtful accounts, net of recoveries                                                                                  | 4              | 11             | 10 | 11 |
| Charge-off of accounts(A)                                                                                                           | (5)            | (3)            | (7) | (6) |
| Financing Receivable, Allowance for Credit Losses, Other                                                                            | 3              | 1              | (1) | 2 |
| Allowance for doubtful accounts at end of period                                                                                    | 62             | 58             | 62 | 58 |
| Loss on Contract Termination for Default                                                                                            | 1              | 1              | 1 | 1 |
| Retail Portfolio [Member]                                                                                                           |           |           |   |   |
| **Financing Receivable, Allowance for Credit Losses [Line Items]**                                                                  |           |           |   |   |
| Allowance for doubtful accounts at beginning of period                                                                              | 22             | 23             | 21 | 27 |
| Provision for doubtful accounts, net of recoveries                                                                                  | 3              | 1              | 7 | (1) |
| Charge-off of accounts(A)                                                                                                           | (3)            | (3)            | (5) | (6) |
| Financing Receivable, Allowance for Credit Losses, Other                                                                            | 0              | 1              | (1) | 2 |
| Allowance for doubtful accounts at end of period                                                                                    | 22             | 22             | 22 | 22 |
| Impaired Financing Receivable, Average Recorded Investment                                                                          |           |           | 16 | 13 |
| Wholesale Portfolio [Member]                                                                                                        |           |           |   |   |
| **Financing Receivable, Allowance for Credit Losses [Line Items]**                                                                  |           |           |   |   |
| Allowance for doubtful accounts at beginning of period                                                                              | 2              | 2              | 2 | 0 |
| Provision for doubtful accounts, net of recoveries                                                                                  | 0              | 0              | 0 | 2 |
| Charge-off of accounts(A)                                                                                                           | 0              | 0              | 0 | 0 |
| Financing Receivable, Allowance for Credit Losses, Other                                                                            | 0              | 0              | 0 | 0 |
| Allowance for doubtful accounts at end of period                                                                                    | 2              | 2              | 2 | 2 |
| Trade and Other Receivables [Member]                                                                                                |           |           |   |   |
| **Financing Receivable, Allowance for Credit Losses [Line Items]**                                                                  |           |           |   |   |
| Allowance for doubtful accounts at beginning of period                                                                              | 36             | 24             | 37 | 24 |
| Provision for doubtful accounts, net of recoveries                                                                                  | 1              | 10             | 3 | 10 |
| Charge-off of accounts(A)                                                                                                           | (2)            | 0              | (2) | 0 |
| Financing Receivable, Allowance for Credit Losses, Other                                                                            | 3              | 0              | 0 | 0 |
| Allowance for doubtful accounts at end of period                                                                                    | $ 38           | $ 34           | $ 38 | $ 34 |

| X                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Classes Of Receivables In Each Portfolio
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing Receivable, Allowance for Credit Losses, Other
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of Portfolio Segments for Finance Receivables
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
A valuation allowance for financing receivables that are expected to be uncollectible.
+ References
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| X                                                                                                                                                                                        |
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of direct write-downs of financing receivables charged against the allowance.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of the loss on termination of a contract for default.
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.
+ References
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