Commitments and Contingencies - Additional Information (Detail)				1 Months Ended				12 Months Ended
	May 08, 2013 ft²	Dec. 15, 2012 ft²	Dec. 06, 2011 ft²	Jun. 30, 2015 ft²	Jan. 31, 2015 ft²	Apr. 30, 2014 ft²	Jan. 31, 2014 ft²	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2017 GBP (£)	Dec. 15, 2016 ft²	Nov. 01, 2013 USD ($) ft²	Nov. 01, 2013 EUR (€) ft²	Sep. 30, 2011 ft²	Jul. 01, 2011 ft²
Commitments And Contingencies Disclosure [Line Items]
Operating lease, rental expense | $								$ 600,000	$ 600,000	$ 800,000
Potential payable amount over the agreement terms based on minimum purchase obligation | $								40,100,000
Further Indication for AMR101 | Marketing Approval In Europe
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment								10,100,000			£ 7,500,000
Further Indication for AMR101 | Potential Marketing Approval 1
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment								6,700,000			5,000,000
Further Indication for AMR101 | Potential Marketing Approval 2
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment								6,700,000			5,000,000
Further Indication for AMR101 | Maximum
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment								13,500,000			£ 10,000,000
Nisshin
Commitments And Contingencies Disclosure [Line Items]
Royalty, milestone or minimum purchase commitments | $								$ 0
Dublin
Commitments And Contingencies Disclosure [Line Items]
Office space leased (in square feet)													270	270	320
Operating lease, expiration date								Oct. 31, 2018
Operating lease, renewal option								1 year
Operating lease, monthly rent													$ 3,500	€ 2,900
Lease termination notice period								3 months
Bedminster
Commitments And Contingencies Disclosure [Line Items]
Office space leased (in square feet)												732				9,747
Operating lease, expiration date								Apr. 30, 2019
Lease termination notice period								6 months
Additional office space leased (in square feet)	10,883	2,601	2,142
Square feet vacated in exchange for reduction on future rent payments						2,000	2,142
Bedminster | Sublease
Commitments And Contingencies Disclosure [Line Items]
Operating lease, expiration date								Sep. 30, 2017
Additional office space leased under sublease (in square feet)				2,500	4,700