Fair Value of Financial Instruments - Fair Value of Financial Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Milestone Rights \| Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	$ 16.5
Financing Liability \| Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	104.4
Liability for Sale of Future Royalties \| Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	92.7
Contingent Milestone Liability \| Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	34.0
Carrying Amount \| Senior Convertible Notes
Financial liabilities:
Total financial liabilities fair value		$ 36.3
Carrying Amount \| Milestone Rights
Financial liabilities:
Total financial liabilities fair value	2.5	2.5
Carrying Amount \| Financing Liability
Financial liabilities:
Total financial liabilities fair value	103.0	103.4
Carrying Amount \| Liability for Sale of Future Royalties
Financial liabilities:
Total financial liabilities fair value	147.8	151.3
Carrying Amount \| Contingent Milestone Liability
Financial liabilities:
Total financial liabilities fair value	$ 34.0	26.2
Estimate of Fair Value Measurement \| Senior Convertible Notes \| Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value		39.3
Estimate of Fair Value Measurement \| Milestone Rights \| Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value		22.0
Estimate of Fair Value Measurement \| Financing Liability \| Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value		121.9
Estimate of Fair Value Measurement \| Liability for Sale of Future Royalties \| Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value		168.1
Estimate of Fair Value Measurement \| Contingent Milestone Liability \| Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value		$ 26.2