Commitments and Contingencies - Additional Information (Detail) - Mar. 31, 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	9.8	£ 7,500,000
Further Indication for AMR101 | Potential Marketing Approval 1
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment	6.5	5,000,000
Further Indication for AMR101 | Potential Marketing Approval 2
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment	6.5	5,000,000
Further Indication for AMR101 | Maximum
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment	$ 13.0	£ 10,000,000