Fair Value of Financial Instruments - Fair Value of Financial Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
MidCap Credit Facility
Financial liabilities:
Financial liabilities fair value	$ 40.7	$ 40.8
Senior Convertible Notes
Financial liabilities:
Financial liabilities fair value	221.6	237.5
Mann Group Convertible Notes
Financial liabilities:
Financial liabilities fair value	33.6	37.8
Milestone Rights Liability
Financial liabilities:
Financial liabilities fair value	17.1	18.1
Carrying Value | MidCap Credit Facility
Financial liabilities:
Financial liabilities fair value	38.9	38.8
Carrying Value | Senior Convertible Notes
Financial liabilities:
Financial liabilities fair value	224.3	223.9
Carrying Value | Mann Group Convertible Notes
Financial liabilities:
Financial liabilities fair value	18.4	18.4
Carrying Value | Milestone Rights Liability
Financial liabilities:
Financial liabilities fair value	5.9	5.9
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | MidCap Credit Facility
Financial liabilities:
Financial liabilities fair value	40.7	40.8
Estimate of Fair Value Measurement | Senior Convertible Notes | Fair Value, Inputs, Level 3
Financial liabilities:
Financial liabilities fair value	221.6	237.5
Estimate of Fair Value Measurement | Mann Group Convertible Notes | Fair Value, Inputs, Level 3
Financial liabilities:
Financial liabilities fair value	33.6	37.8
Estimate of Fair Value Measurement | Milestone Rights Liability | Fair Value, Inputs, Level 3
Financial liabilities:
Financial liabilities fair value	$ 17.1	$ 18.1