License and Collaboration Agreements - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended			3 Months Ended	9 Months Ended					0 Months Ended	9 Months Ended	3 Months Ended		9 Months Ended			0 Months Ended			3 Months Ended	0 Months Ended	3 Months Ended		9 Months Ended		0 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 Baxter [Member] License and Collaboration Agreements [Member]	Sep. 30, 2014 Baxter [Member] License and Collaboration Agreements [Member]	Sep. 30, 2014 Baxter [Member] License and Collaboration Agreements [Member] Research and Development Milestones [Member]	Sep. 30, 2014 Baxter [Member] License and Collaboration Agreements [Member] Regulatory Milestones [Member]	Sep. 30, 2014 Baxter [Member] License and Collaboration Agreements [Member] Sales Milestone [Member]	Sep. 30, 2014 Baxter [Member] License and Collaboration Agreements [Member] Clinical Trials in Pancreatic Cancer [Member]	Nov. 10, 2009 Sanofi [Member]	Sep. 30, 2014 Sanofi [Member]	Sep. 30, 2014 Sanofi [Member] License and Collaboration Agreements [Member]	Sep. 30, 2013 Sanofi [Member] License and Collaboration Agreements [Member]	Sep. 30, 2014 Sanofi [Member] License and Collaboration Agreements [Member]	Sep. 30, 2013 Sanofi [Member] License and Collaboration Agreements [Member]	Dec. 31, 2013 Sanofi [Member] License and Collaboration Agreements [Member]	May 05, 2011 Pharma Engine [Member]	May 05, 2011 Pharma Engine [Member] Sales Milestone [Member]	May 05, 2011 Pharma Engine [Member] Development and Regulatory Milestone [Member]	Mar. 31, 2012 Pharma Engine [Member] Phase 3 Clinical Trial in Pancreatic Cancer [Member]	Sep. 22, 2014 Pharma Engine [Member] License and Collaboration Agreements [Member]	Sep. 30, 2014 Pharma Engine [Member] License and Collaboration Agreements [Member]	Sep. 30, 2013 Pharma Engine [Member] License and Collaboration Agreements [Member]	Sep. 30, 2014 Pharma Engine [Member] License and Collaboration Agreements [Member]	Sep. 30, 2013 Pharma Engine [Member] License and Collaboration Agreements [Member]	Sep. 22, 2014 Pharma Engine [Member] License and Collaboration Agreements [Member] New Drug Application [Member]	Sep. 30, 2014 Actavis [Member]	Dec. 31, 2013 Actavis [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront license fee received							$ 100,000,000					$ 60,000,000
Milestone license fee received								100,000,000	520,000,000	250,000,000			25,000,000																2,900,000
Milestone payment											98,800,000											5,000,000	7,000,000					5,000,000
Royalty for improved products							The Company is also entitled to tiered, escalating royalties ranging from sub-teen double-digits to low twenties percentages of net sales of MM-398 in the Licensed Territory.
Notice period of termination							180 days																						90 days
Company recognized revenue	28,002,000	6,856,000	68,851,000	39,963,000		0	0							28,002,000	6,856,000	68,851,000	39,410,000
Deferred revenue						100,000,000	100,000,000							21,236,000		21,236,000		73,392,000
Deferred revenue, current	68,737,000		68,737,000		9,336,000	47,500,000	47,500,000
Agreement termination scheduled date			Dec. 17, 2014
Expected development period from the effective date of agreement												12 years
Development services performed																5,800,000
Upfront license fees paid																			10,000,000
Maximum milestone payment obligation																				130,000,000	80,000,000
Milestone payment due date																							Apr. 30, 2015
Research and development expenses	43,632,000	37,630,000	107,751,000	117,084,000																				12,400,000	500,000	12,500,000	1,000,000
Eligible milestone payments																													15,500,000
Agreement expiration term respect to each product																													10 years
Additional renewal term																													2 years
Milestones and development expenses																													$ 3,800,000	$ 2,100,000