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Summary of Significant Accounting Policies - Narrative (Detail) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020
Minimum |  |  |  |  |
Schedule Of Significant Accounting Policies [Line Items] |  |  |  |  |
Additional terms of termination option |  |  | 1 year |  |
Maximum |  |  |  |  |
Schedule Of Significant Accounting Policies [Line Items] |  |  |  |  |
Additional terms of termination option |  |  | 10 years |  |
GE | Credit Concentration Risk | Receivables |  |  |  |  |
Schedule Of Significant Accounting Policies [Line Items] |  |  |  |  |
Concentration risk (in percentage) |  |  | 10.00% |  | 16.00%
GE | Revenue Concentration Risk | Revenue From Contract With Customer |  |  |  |  |
Schedule Of Significant Accounting Policies [Line Items] |  |  |  |  |
Concentration risk (in percentage) | 9.00% | 12.00% | 10.00% | 13.00% |

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