Commitments and Contingencies - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended					124 Months Ended	12 Months Ended					1 Months Ended				12 Months Ended				12 Months Ended		1 Months Ended		12 Months Ended	1 Months Ended		12 Months Ended			12 Months Ended							12 Months Ended							24 Months Ended		1 Months Ended	12 Months Ended					12 Months Ended						12 Months Ended			12 Months Ended		1 Months Ended	12 Months Ended				12 Months Ended							12 Months Ended			1 Months Ended	12 Months Ended
	Jan. 12, 2011	May 27, 2010	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2007	Dec. 31, 2013	Dec. 31, 2013 Harmon Hill LLC Collaboration Agreement	Dec. 31, 2012 Harmon Hill LLC Collaboration Agreement	Dec. 31, 2011 Harmon Hill LLC Collaboration Agreement	Dec. 31, 2010 Harmon Hill LLC Collaboration Agreement	Jun. 27, 2013 Harmon Hill LLC Collaboration Agreement	Apr. 08, 2008 Harmon Hill LLC Collaboration Agreement Upon the dosing of the first patient	Jun. 27, 2013 Harmon Hill LLC Monthly Payment Collaboration Agreement	Apr. 08, 2008 Harmon Hill LLC Monthly Payment Collaboration Agreement	Mar. 07, 2011 Solasia	Dec. 31, 2013 Solasia Development-based milestones	Dec. 31, 2013 Solasia Sales-based milestones	Dec. 31, 2004 DEKK Tec Inc	Oct. 15, 2004 DEKK Tec Inc	Dec. 31, 2006 DEKK Tec Inc Upon the dosing of the first patient	Dec. 31, 2010 DEKK Tec Inc Phase 3	Mar. 16, 2010 DEKK Tec Inc Upon receiving a United States Patent for palifosfamide	Oct. 15, 2004 DEKK Tec Inc Up Front Payment	Dec. 31, 2013 Intrexon Corporation	Jan. 06, 2011 Intrexon Corporation Quarterly Payment	Aug. 24, 2004 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System Patent	Dec. 31, 2007 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System	Dec. 31, 2004 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System	Dec. 31, 2013 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System	Dec. 31, 2005 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System Upon the commencement of Phase 1 clinical trial	Dec. 31, 2006 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System Upon the dosing of the first patient	Dec. 31, 2007 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System Intellectual Property Rights	Dec. 31, 2006 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System Intellectual Property Rights	Dec. 31, 2005 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System Upon the filing of an Investigation New Drug application (IND) for darinaparsin	Dec. 31, 2007 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System Upon the completion of dosing of the last patient for both Phase 1 clinical trials	Dec. 31, 2013 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System Upon enrollment of the first patient in a multi-center pivotal clinical trial	Dec. 31, 2004 The University of Texas M.D. Anderson Cancer Center and The Texas A & M University System Up Front Payment	Dec. 31, 2013 Southern Research Institute	Dec. 31, 2012 Southern Research Institute	Dec. 31, 2011 Southern Research Institute	Dec. 31, 2010 Southern Research Institute	Dec. 31, 2009 Southern Research Institute	Dec. 31, 2008 Southern Research Institute	Dec. 22, 2006 Southern Research Institute Execution Agreement	Dec. 22, 2006 Southern Research Institute Maximum	Nov. 03, 2006 Baxter Healthcare Corporation	Dec. 31, 2007 Baxter Healthcare Corporation Upon the successful U.S. IND application for indibulin	Nov. 03, 2006 Baxter Healthcare Corporation Assets	Nov. 03, 2006 Baxter Healthcare Corporation Inventories	Nov. 03, 2006 Baxter Healthcare Corporation Royalty Payments	Jan. 29, 2010 PPD Development L. P.	Dec. 31, 2010 PPD Development L. P. Upon a clinical study commencement of enrollment in North America	Dec. 31, 2011 PPD Development L. P. Upon contract execution	Dec. 31, 2010 PPD Development L. P. Upon contract execution	Dec. 31, 2012 PPD Development L. P. Upon initial clinical study enrollment	Dec. 31, 2013 PPD Development L. P. Upon the achievement of various milestones	Dec. 31, 2011 Pharmaceutical Research Associates Inc	Dec. 31, 2013 Pharmaceutical Research Associates Inc Upon the achievement of various milestones	Dec. 31, 2012 Pharmaceutical Research Associates Inc Upon the achievement of various milestones	Nov. 02, 2012 Novella Clinical, Inc.	Dec. 31, 2012 Novella Clinical, Inc. Upon the achievement of various milestones	Dec. 31, 2013 Novella Clinical, Inc. Upon two database related milestones	Oct. 17, 2013 NEW YORK sqft	Dec. 31, 2013 NEW YORK	Dec. 31, 2012 NEW YORK sqft	Jan. 31, 2012 NEW YORK sqft	Dec. 31, 2011 NEW YORK sqft	Dec. 31, 2011 Boston, MA	Dec. 31, 2012 Boston, MA	Dec. 31, 2011 Boston, MA The first floor sqft	Jun. 30, 2012 Boston, MA The second floor sqft	Dec. 31, 2011 Boston, MA The second floor sqft	Dec. 31, 2011 Boston, MA The third floor sqft	Jun. 30, 2012 Boston, MA The four floor sqft	Dec. 31, 2012 Germantown, MD	Dec. 31, 2011 Germantown, MD	Apr. 30, 2011 Germantown, MD sqft	Aug. 30, 2013 Boston MA Office sqft	Dec. 31, 2013 Boston MA Office sqft
Commitments and Contingencies Disclosure [Line Items]
Office space under operating lease																																																																			7,259		6,251				4,113			9,800			2,227		21,184
Letter of credit																																																																		$ 388,000	$ 388,000		$ 388,000
Additional office space under operating lease																																																																				1,008
Operating lease expiration month and year																																																																		2018-10	2018-10			2016-08								2014-03
Area under sublease agreement																																																																	7,259															5,249
Loss on sublease																																																																		729,000															42,000
Remaining contractual obligation																																																																		2,300,000															367,000
Sublease revenue from subtenant																																																																		1,600,000															325,000
Loss on disposal of fixed assets			(585,000)	(48,000)	0			(641,000)																																																										(392,000)															(194,000)
Operating lease space																																																																								5,249		8,538	6,959
Security deposits																																																																							127,000					41,000		4,000		20,000	127,000
Security deposit from subtenant																																																																																	20,000
Office closing date																																																																													Jul. 16, 2012
Total rent Expense			1,000,000	1,100,000	647,000			5,200,000
Deferred rent liability - current			212,000	39,000				212,000
Deferred rent liability - long term			851,000	400,000				851,000
Deferred rent liability net			1,100,000	439,000				1,100,000
Number of products																												2
Licensing fee																									50,000														125,000
Shares of common stock granted			2,649,900	2,309,650	1,894,300																									250,487
Option to purchase common stock		1,050,000																		27,616										50,222
Sale of stock ,price per share																				$ 0.02										$ 0.002
Shares vested																				6,904																12,555	25,111
Stock based compensation expenses			3,507,000	4,880,000	2,759,000			23,688,000																					120,000
Shares expected to vest																																						12,556
Milestone payment																						100,000	300,000	100,000								100,000	250,000	100,000	100,000														625,000					1,100,000	4,000,000	1,800,000	3,800,000	9,200,000		2,200,000	7,300,000		256,000	136,000
Milestone maximum payment																					4,000,000										4,500,000									775,000												8,000,000	20,000,000						9,500,000			790,000
Shares vested						6,904	25,111																6,904
Research expenses	17,500,000		42,852,000	83,446,000	57,083,000			255,197,000																																						25,000	200,000
Royalty payment																																								25,000	25,000	25,000	25,000	25,000	25,000
Asset Purchase Agreement, upfront cash payment																																																		1,100,000	100,000
Annual patent and license prosecution/maintenance fee																																																15,000
Milestones under the license agreement expense			250,000	250,000	0	0
Percent of company net profit									1.00%																		50.00%
Percentage of revenue agreed to pay which is obtained from sublicensor																											50.00%
Contract termination description																										Our obligation to pay 50% of net profits or revenue described above with respect to these "retained" products will survive termination of the Channel Agreement.
Other expense									135,000	200,000	240,000	240,000
Payment for consulting services fee														500,000	15,000	20,000
Agreement term													1 year
Upfront payment received																	5,000,000
Expected Additional milestone payments to be received																		$ 32,500,000	$ 53,500,000