Fair Value of Financial Instruments - Fair Value of Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
MidCap Credit Facility
Financial liabilities:
Total financial liabilities fair value	$ 40.8	$ 55.4
Senior convertible notes
Financial liabilities:
Total financial liabilities fair value	237.5
Mann Group Convertible Notes
Financial liabilities:
Total financial liabilities fair value	37.8	52.2
Milestone Rights Liability
Financial liabilities:
Total financial liabilities fair value	18.1	19.8
2024 Convertible Notes
Financial liabilities:
Total financial liabilities fair value		7.0
Mann Group Promissory Notes
Financial liabilities:
Total financial liabilities fair value		78.9
PPP Loan
Financial liabilities:
Total financial liabilities fair value		4.7
Carrying Amount | MidCap Credit Facility
Financial liabilities:
Total financial liabilities fair value	38.8	49.3
Carrying Amount | Senior convertible notes
Financial liabilities:
Total financial liabilities fair value	223.9
Carrying Amount | Mann Group Convertible Notes
Financial liabilities:
Total financial liabilities fair value	18.4	28.0
Carrying Amount | Milestone Rights Liability
Financial liabilities:
Total financial liabilities fair value	5.9	7.3
Carrying Amount | 2024 Convertible Notes
Financial liabilities:
Total financial liabilities fair value		5.0
Carrying Amount | Mann Group Promissory Notes
Financial liabilities:
Total financial liabilities fair value		63.0
Carrying Amount | PPP Loan
Financial liabilities:
Total financial liabilities fair value		4.9
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | MidCap Credit Facility
Financial liabilities:
Total financial liabilities fair value	40.8	55.4
Estimate of Fair Value Measurement | Senior convertible notes | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	237.5
Estimate of Fair Value Measurement | Mann Group Convertible Notes | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	37.8
Estimate of Fair Value Measurement | Milestone Rights Liability | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	$ 18.1	19.8
Estimate of Fair Value Measurement | 2024 Convertible Notes | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value		7.0
Estimate of Fair Value Measurement | Mann Group Promissory Notes | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value		78.9
Estimate of Fair Value Measurement | PPP Loan | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value		$ 4.7