Commitments and Contingencies - Collaboration Agreements (Details) $ in Millions		1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Aug. 03, 2020 USD ($) Option	Aug. 31, 2021	Apr. 30, 2020 USD ($)	Jun. 30, 2019	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Development milestone payment					$ 0.0		$ 0.0
Catalent Maryland, Inc. (Catalent)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Annual fee payable, term				5 years
Period for which annual fee is payable			5 years
Term of manufacturing and supply agreement			5 years
Additional extension term of manufacturing and supply agreement			5 years
Minimum amount agreed to purchase in batches of drug product			$ 10.6
Amended and restated agreement with Penn
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Annual fee payable	$ 5.0
Quarterly fee payable	$ 1.3
Number of CNS indications | Option	8
Upfront payments	$ 1.0
Upfront fee payable upon clinical candidate designation	0.5
Upfront fee due	$ 0.5
Payments for technology license fee						$ 5.0			$ 5.0
Additional technology license fee paid					1.5		3.0	$ 0.5	$ 1.5
Payment made on option exercise						$ 0.5		$ 0.5
Amount payable per product candidate arising from the exploratory program for large CNS indications					39.0		39.0
Sales milestone payments					55.0		55.0
Amended and restated agreement with Penn | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, tiered transaction fee percent		1.00%
Amended and restated agreement with Penn | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, tiered transaction fee percent		2.00%
Amount payable per product candidate for rare, monogenic disorders					$ 16.5		$ 16.5