| **Commitments and contingencies (Details)**                                                                       | 1 Months Ended |            | 0 Months Ended | 3 Months Ended | 0 Months Ended | 12 Months Ended |            |              |            |            | 3 Months Ended | 6 Months Ended | 3 Months Ended |               | 3 Months Ended    |
|-------------------------------------------------------------------------------------------------------------------|----------------|------------|----------------|----------------|----------------|-----------------|------------|--------------|------------|------------|----------------|----------------|----------------|---------------|-------------------|
||
| **Loss Contingencies [Line Items]**                                                                               |           |       |           |           |           |            |       |         |       |       |           |           |           |          |              |   |   |   |
| Length of Agreement                                                                                               |           |       |           |           |           |            |       |         |       |       |           |           |           |          | 3 years           |   |   |   |
| Length Of Potential Automatic Extension Years                                                                     |           |       |           |           |           |            |       |         |       |       |           |           |           |          | 1 year            |   |   |   |
| Operating Agreement Excess Loss Percentage                                                                        |           |       |           |           |           |            |       |         |       |       |           |           |           |          | 10.00%            |   |   |   |
| Outstanding finance receivables, off-balance sheet                                                                |           |       |           |           |           |            |       |         |       |       |           |           |           |          | $ 1,043,000,000   | $ 723,000,000 |   |   |
| Related originations of outstanding finance receivables, off-balance sheet                                        |           |       |           |           |           |            |       |         |       |       |           |           |           |          | 1,240,000,000,000 | 818,000,000 |   |   |
| Historical losses on finance receivables, measured as percentage of average balance of related finance receivable |           |       |           |           |           |            |       |         |       |       |           |           |           |          |              |   | 0.30% | 2.10% |
| Available stand-by letters of credit and surety bonds                                                             |           | 98,000,000 |           |           |           |            |       |         |       |       |           |           |           |          |              |   |   |   |
| Unused credit commitments outstanding                                                                             |           | 33,000,000 |           |           |           |            |       |         |       |       |           |           |           |          |              |   |   |   |
| Purchase commitments                                                                                              | 127,000,000    |       |           |           |           |            |       |         |       |       |           |           |           |          |              |   |   |   |
| Long Term Purchase Commitment Cancellation Fees                                                                   | 30,000,000     |       |           |           |           |            |       |         |       |       |           |           |           |          |              |   |   |   |
| Number of Contaminated Sites                                                                                      |           | 2          |           |           |           |            |       |         |       |       |           |           |           |          |              |   |   |   |
| Accrual for environmental loss contingencies                                                                      |           | 20,000,000 |           |           |           |            |       |         |       |       |           |           |           |          |              |   |   |   |
| Damages sought, value                                                                                             |           |       | 1,050,000      | 2,000,000      | 5,700,000      | 10,850,000      | 42,000,000 |         |       |       |           |           | 10,000,000     | 1,919,000,000 |              |   |   |   |
| Notive of Violation, number                                                                                       |           |       |           |           |           |            |       |         |       |       | 7,600          |           |           |          |              |   |   |   |
| Potential patent infringement, number of patents                                                                  |           |       |           |           |           |            |       |         |       |       |           | 3              |           |          |              |   |   |   |
| Estimate of possible loss                                                                                         |           |       |           |           |           |            | 16,000,000 | $ 38,800,000 | 74,000,000 | 70,000,000 |           |           |           |          |              |   |   |   |

| X                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Historic Losses On Finance Receivables Measured As Percentage Of Average Balance Of Related Finance Receivable
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| X                                                                                                                                                                                                                               |
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| - Definition
Length of Agreement
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| X                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Length Of Potential Automatic Extension Years
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| X                                                                                                                                                                                                                                                |
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| - Definition
Cancellation Fees
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| X                                                                                                                                                                                                                                                                                                            |
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| - Definition
Loss Contingency, Potential Patent Infringement, Number of Patents
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Notive of Violation, number
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Number of Contaminated Sites
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| X                                                                                                                                                                                                                                                                     |
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| - Definition
Off Balance Sheet Risks Finance Receivables
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| X                                                                                                                                                                                                                                                                                                             |
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| - Definition
Off Balance Sheet Risks Finance Receivables Related Originations
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| X                                                                                                                                                                                                                                                               |
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| - Definition
Operating Agreement Excess Loss Percentage
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| X                                                                                                                                                                                                                                                            |
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| - Definition
Unused Credit Commitments Outstanding
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Total costs accrued as of the balance sheet date for environmental loss contingencies.
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| - Definition
The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.
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| X                                                                                                                                                                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The minimum amount the entity agreed to spend under the long-term purchase commitment.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The value (monetary amount) of the award the plaintiff seeks in the legal matter.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.
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