Fair Value of Financial Instruments - Fair Value of Financial Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Carrying Amount | Senior Convertible Notes
Financial liabilities:
Total financial liabilities fair value	$ 36.1	$ 36.1
Carrying Amount | Milestone Rights
Financial liabilities:
Total financial liabilities fair value	2.5	3.2
Carrying Amount | Financing Liability
Financial liabilities:
Total financial liabilities fair value	103.8	103.9
Carrying Amount | Liability for Sale of Future Royalties
Financial liabilities:
Total financial liabilities fair value	150.2	149.6
Estimate of Fair Value Measurement | Senior Convertible Notes | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	39.4	46.9
Estimate of Fair Value Measurement | Milestone Rights | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	15.7	19.2
Estimate of Fair Value Measurement | Financing Liability | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	117.1	117.4
Estimate of Fair Value Measurement | Liability for Sale of Future Royalties | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	$ 157.4	$ 156.7