Organization - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2020 USD ($) Subsidiary	Dec. 31, 2019 USD ($)
Organization [Line Items]
Number of subsidiaries | Subsidiary	3
Working capital	$ 15,000,000
Accumulated deficit	594,002,000	$ 585,621,000
Cash, cash equivalents and marketable securities	$ 33,620,000	$ 47,745,000
EUSA
Organization [Line Items]
Percentage of EUSA cost-sharing for TIVO-3 trial	50.00%
EUSA | Maximum
Organization [Line Items]
Potential additional reimbursement milestones	$ 4,000,000
EUSA | Marketing Approval in France, Italy, Spain and the United Kingdom
Organization [Line Items]
Milestone payment to be received	2,000,000
EUSA | Marketing Approval in Australia, Brazil, New Zealand, South Africa and Switzerland
Organization [Line Items]
Milestone payment to be received	$ 2,000,000
Kyowa Hakko Kirin
Organization [Line Items]
Percentage of sublicense fee payable	30.00%
Kyowa Hakko Kirin | Maximum
Organization [Line Items]
Research and development reimbursement, potential opt-in payment	$ 20,000,000