Nature of the Business and Summary of Significant Accounting Policies - Additional Information (Detail)			1 Months Ended			12 Months Ended
	Dec. 03, 2019 USD ($)	May 07, 2019 USD ($)	Jul. 25, 2019 USD ($)	Jul. 12, 2019 USD ($)	May 31, 2019 USD ($)	Dec. 31, 2019 USD ($) Segment Region	Dec. 31, 2018 USD ($)	Nov. 29, 2019 USD ($)	Apr. 15, 2019 USD ($)	Apr. 30, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of equity securities						$ 51,500,000	$ 52,500,000
Proceeds from sale of research and development operations						2,025,000	75,000
Special cash dividend paid	$ 6,700,000		$ 20,000,000
Dividend payable date	Dec. 23, 2019		Sep. 05, 2019
Dividend payable, date of record	Dec. 16, 2019		Aug. 28, 2019
Accumulated deficit						540,609,000	523,277,000
Net loss from continuing operations						21,267,000	60,767,000
Cash in continuing operations for operating activities						31,368,000	65,588,000
Cash, cash equivalents and marketable securities						$ 16,600,000
Number of operating segments | Segment						1
Number of geographic regions | Region						1
Original maturities						Three months or less
Restricted cash						$ 0	600,000
Other income (expense), net						370,000	(3,230,000)
Silver Creek Pharmaceuticals, Inc. [Member]
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of equity securities		$ 7,800,000			$ 7,800,000
Other income (expense), net						400,000	(3,200,000)
Other nonoperating gains (losses)						$ 1,400,000
Silver Creek Pharmaceuticals, Inc. [Member] | Laboratory Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of research and development operations					$ 1,400,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected original maturities period of marketable securities classified as available-for-sale						90 days
Loan Agreement [Member] | Hercules Capital, Inc [Member] | Term Loan [Member]
Summary Of Significant Accounting Policies [Line Items]
Payoff amount							$ 16,000,000		$ 16,000,000
Ipsen [Member] | First Line Treatment of Metastatic Adenocarcinoma of Pancreas [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable										$ 225,000,000
Ipsen [Member] | After Failure of First Line Chemotherapy [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable										150,000,000
Ipsen [Member] | Additional Indication [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable										75,000,000
Ipsen [Member] | Ongoing Multi Part Clinical [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable								$ 5,000,000
Ipsen [Member] | Asset Sale Agreement [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable										$ 450,000,000
14ner Sale [Member]
Summary Of Significant Accounting Policies [Line Items]
Upfront cash payment received				$ 3,500,000
14ner Sale [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional payments receivable on achievement of certain milestone events				54,500,000
14ner Sale [Member] | Maximum [Member] | Achievement of the Primary Endpoint in the First Registrational Clinical Study of Either MM-121 or MM-111 [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional payments receivable on achievement of certain milestone events				3,000,000
14ner Sale [Member] | Maximum [Member] | Achievement of Various Regulatory Approval and Reimbursement-Based Milestones in the United States, Europe and Japan [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional payments receivable on achievement of certain milestone events				16,500,000
14ner Sale [Member] | Maximum [Member] | Achievement Various Cumulative Worldwide Net Sales Targets Between $100.0 million and $300.0 million for MM-121 and MM-111 [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional payments receivable on achievement of certain milestone events				35,000,000
Cumulative worldwide net sales target				$ 300,000,000