Marketable Securities - Cash Equivalents (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents		$ 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money Market Funds | Maximum
Assets:
Cash equivalents	$ 100
Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents		$ 100