Fair Value of Financial Instruments - Fair Value of Financial Instruments (Parenthetical) (Detail) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2026 USD ($)	Dec. 31, 2025 USD ($)
Fair Value Of Financial Instruments [Line Items]
Operating lease weighted average discount rate	7.60%	7.60%
Senior Convertible Notes
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of hypothetical yield		5
Note payable, percentage of interest rate increases (decreases)		2.00%
Senior Convertible Notes \| Volatility
Fair Value Of Financial Instruments [Line Items]
Note payable, fair value key inputs		40.3
Senior Convertible Notes \| Minimum
Fair Value Of Financial Instruments [Line Items]
Financial liabilities fair value		$ 39.0
Senior Convertible Notes \| Maximum
Fair Value Of Financial Instruments [Line Items]
Financial liabilities fair value		$ 39.5
Milestone Rights \| Risk-Free Rate
Fair Value Of Financial Instruments [Line Items]
Note payable, fair value key inputs	5.15	3.94
Milestone Rights \| Dividend Yield
Fair Value Of Financial Instruments [Line Items]
Note payable, fair value key inputs	0	0
Milestone Rights \| Volatility
Fair Value Of Financial Instruments [Line Items]
Note payable, fair value key inputs	43	43
Milestone Rights \| Period
Fair Value Of Financial Instruments [Line Items]
Note payable, fair value key inputs	7	7
Milestone Rights \| Credit Risk
Fair Value Of Financial Instruments [Line Items]
Note payable, fair value key inputs	11.7	10
Financing Liability
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of hypothetical yield	10	7
Note payable, percentage of interest rate increases (decreases)	2.00%	2.00%
Financing Liability \| Minimum
Fair Value Of Financial Instruments [Line Items]
Financial liabilities fair value	$ 90.5	$ 106.7
Financing Liability \| Maximum
Fair Value Of Financial Instruments [Line Items]
Financial liabilities fair value	$ 114.0	$ 140.6
Liability for Sale of Future Royalties
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of hypothetical yield	11	8
Note payable, percentage of interest rate increases (decreases)	2.00%	2.00%
Liability for Sale of Future Royalties \| Minimum
Fair Value Of Financial Instruments [Line Items]
Financial liabilities fair value	$ 82.5	$ 148.3
Liability for Sale of Future Royalties \| Maximum
Fair Value Of Financial Instruments [Line Items]
Financial liabilities fair value	$ 97.8	192.3
Milestone 1
Fair Value Of Financial Instruments [Line Items]
Financial liabilities fair value		$ 23.7
Probability of Achievement of Regulatory Approval, Percentage		85.00%
Operating lease weighted average discount rate		10.00%
Change In Estimate Of Probability And Discount Rate		2.00%
Milestone 1 \| Minimum
Fair Value Of Financial Instruments [Line Items]
Financial liabilities fair value		$ 24.7
Milestone 1 \| Maximum
Fair Value Of Financial Instruments [Line Items]
Financial liabilities fair value		$ 22.7
Milestone 2
Fair Value Of Financial Instruments [Line Items]
Note payable, fair value key inputs		25.2
Note payable, percentage of interest rate increases (decreases)	2.00%
Financial liabilities fair value	$ (0.0)	$ 2.6
Operating lease weighted average discount rate	11.70%	10.00%
Change In Estimate Of Probability And Discount Rate		2.00%
Milestone 2 \| Volatility
Fair Value Of Financial Instruments [Line Items]
Note payable, fair value key inputs	16.6
Milestone 2 \| Minimum
Fair Value Of Financial Instruments [Line Items]
Financial liabilities fair value		$ 2.6
Milestone 2 \| Maximum
Fair Value Of Financial Instruments [Line Items]
Financial liabilities fair value		$ 2.7

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