Commitments and Contingencies - Additional Information (Detail) - Sep. 30, 2019 $ in Millions	USD ($)	GBP (£)
Commitments And Contingencies Disclosure [Line Items]
Potential payable amount over the agreement terms based on minimum purchase obligation	$ 90.0
Further Indication for AMR101 | Marketing Approval In Europe
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment	9.2	£ 7,500,000
Further Indication for AMR101 | Potential Marketing Approval 1
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment	6.1	5,000,000
Further Indication for AMR101 | Potential Marketing Approval 2
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment	6.1	5,000,000
Further Indication for AMR101 | Maximum
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment	$ 12.3	£ 10,000,000