Collaboration, Licensing and Milestone Agreements - Additional Information (Detail)	1 Months Ended								3 Months Ended	12 Months Ended
	Nov. 30, 2018 EUR (€)	Nov. 30, 2018 USD ($)	Sep. 30, 2017 EUR (€)	Sep. 30, 2017 USD ($)	May 31, 2017 EUR (€)	May 31, 2017 USD ($)	Jan. 31, 2014 USD ($)	Mar. 31, 2000	Jun. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	May 31, 2017 USD ($)	Apr. 30, 2017 USD ($)	Oct. 31, 2016 USD ($)	Sep. 30, 2014 USD ($)	May 31, 2012 USD ($)	Jun. 30, 2005 USD ($)	Nov. 30, 1998 USD ($)
University of Vermont | PIXUVRI
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Period from first commercial sale								10 years
Collaborative Arrangement Product Agreement | Cephalon, Inc | Products
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingency milestone payment to be received																	$ 100,000,000.0
Milestone payments received										$ 60,000,000
Collaborative Arrangement Product Agreement | Novartis | Products
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingency milestone payment to be made							$ 16,600,000.0
Percentage of royalty payable to net sales							10.00%
Collaborative Arrangement Product Agreement | Gynecologic Oncology Group
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestones obligation paid									$ 500,000
Collaborative Arrangement Product Agreement | PG-TXL
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingency milestone payment to be made																		$ 14,400,000.0
Asset Return and Termination Agreement | Borrowing Associated With License Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingency milestone payment to be made														$ 10,300,000
S_BIO Asset Purchase Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingency milestone payment to be made																$ 132,500,000.0
Milestone payments through the issuance of stock																50.00%
Servier | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Consideration received					€ 12,000,000	$ 12,800,000
Revenue recognized	€ 3,000,000	$ 3,400,000	€ 1,000,000	$ 1,200,000	2,000,000
Contingency milestone payment to be received | €					76,000,000
Potential regulatory milestone payment | €					36,000,000
Potential sales based milestone payment | €					€ 40,000,000
Servier | Collaborative Arrangement | License
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized											$ 11,500,000
Servier | Collaborative Arrangement | Development and Other Services
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized										1,400,000	500,000
Deferred revenue												$ 1,300,000	$ 1,900,000		$ 600,000
FDA Approval | Collaborative Arrangement Product Agreement | Cephalon, Inc | Products
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized										10,000,000
Worldwide Net Sales | Collaborative Arrangement Product Agreement | Cephalon, Inc | Products
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized										$ 10,000,000	$ 10,000,000