Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 147,624	$ 139,514
Unremitted earnings	0	0
Unrecognized Tax Benefits	$ 1,517	$ 0	$ 369
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Utilization of tax losses	80.00%
Atai Therapeutics Pty Ltd [Member]
Operating Loss Carryforwards [Line Items]
Corporate income tax	30.00%
Amount of passive income exceed	90.00%
Germany \| Weighted Average [Member]
Operating Loss Carryforwards [Line Items]
Corporate income tax	30.18%	30.18%
Corporate tax rate	15.00%	15.00%
Solidarity surcharge	0.83%	0.83%
Trade tax rate	14.35%	14.35%
US \| Weighted Average [Member]
Operating Loss Carryforwards [Line Items]
Corporate income tax	21.00%	21.00%
Australia \| Weighted Average [Member]
Operating Loss Carryforwards [Line Items]
Corporate income tax	25.00%	25.00%
United Kingdom \| Weighted Average [Member]
Operating Loss Carryforwards [Line Items]
Corporate income tax	25.00%	25.00%
Canada
Operating Loss Carryforwards [Line Items]
Corporate income tax	26.50%	26.50%
Netherlands [Member]
Operating Loss Carryforwards [Line Items]
Corporate income tax	16.00%