Fair Value of Financial Instruments - Fair Value of Financial Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Carrying Amount | MidCap Credit Facility
Financial liabilities:
Total financial liabilities fair value		$ 33.0
Carrying Amount | Senior Convertible Notes
Financial liabilities:
Total financial liabilities fair value	$ 227.6	226.9
Carrying Amount | Mann Group Convertible Note
Financial liabilities:
Total financial liabilities fair value		8.8
Carrying Amount | Milestone Rights
Financial liabilities:
Total financial liabilities fair value	3.9	3.9
Carrying Amount | Contingent Milestone Liability
Financial liabilities:
Total financial liabilities fair value	0.3	0.3
Carrying Amount | Financing Liability
Financial liabilities:
Total financial liabilities fair value	104.0	104.1
Carrying Amount | Liability for Sale of Future Royalties
Financial liabilities:
Total financial liabilities fair value	147.5
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | MidCap Credit Facility
Financial liabilities:
Total financial liabilities fair value		35.5
Estimate of Fair Value Measurement | Senior Convertible Notes | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	258.9	231.3
Estimate of Fair Value Measurement | Mann Group Convertible Note | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value		14.4
Estimate of Fair Value Measurement | Milestone Rights | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	10.6	11.9
Estimate of Fair Value Measurement | Contingent Milestone Liability | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	0.3	0.3
Estimate of Fair Value Measurement | Financing Liability | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	106.6	$ 106.8
Estimate of Fair Value Measurement | Liability for Sale of Future Royalties | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	$ 163.9