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Leases - Costs (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
Leases - Costs (Details) - USD ($) $ in Millions	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Leases
Total lease costs	$ 0.3	$ 0.1
Weighted-average incremental borrowing rate used to determine right-of-use assets and lease liabilities	11.00%
Impairment losses of ROU assets	$ 0.0		$ 0.0
Clinical site equipment
Leases
Weighted-average incremental borrowing rate used to determine right-of-use assets and lease liabilities	7.00%
Maximum
Leases
Short-term operating lease costs	$ 0.1	$ 0.1