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Fair Value Measurements - Narrative (Details) - USD ($) | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Aug. 31, 2020 | Sep. 30, 2020 | Sep. 30, 2021
Fair Value Disclosures [Abstract] |  |  |
Assets held for sale, fair value |  | $ 0 | $ 0
MSP termination benefits payment | $ 5,175,000 | $ 5,175,000 |
Deferred retirement benefit |  |  | $ 0

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