Summary of Significant Accounting Policies - ASC 606 Adoption (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Impact due to new accounting pronouncements
Retained earnings	$ 830,989	$ 775,829
Effect of the Effect of ASU 606 \| ASU 2014-09
Impact due to new accounting pronouncements
Retained earnings		$ 5,200

The cumulative amount of the reporting entity's undistributed earnings or deficit.

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