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Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Estimated fair value of the convertible notes		$ 187.9
LEVEL 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Estimated fair value of the convertible notes	$ 283.6