Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended				127 Months Ended	3 Months Ended	12 Months Ended					1 Months Ended				3 Months Ended		1 Months Ended	12 Months Ended			12 Months Ended							12 Months Ended				12 Months Ended			1 Months Ended		3 Months Ended	12 Months Ended					24 Months Ended		1 Months Ended	12 Months Ended			12 Months Ended						12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	1 Months Ended		12 Months Ended		1 Months Ended	12 Months Ended					1 Months Ended	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2014	Mar. 31, 2014 Harmon Hill LLC Collaboration Agreement	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	Mar. 31, 2014 Solasia Development-based milestones	Mar. 31, 2014 Solasia Sales-based milestones	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	Mar. 31, 2014 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	Mar. 31, 2014 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, 2005 DEKK Tec Inc	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, 2011 DEKK Tec Inc Phase 3	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	Mar. 31, 2014 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 Royalty Payments	Jan. 29, 2010 PPD Development L. P.	Dec. 31, 2011 PPD Development L. P. Upon contract execution	Dec. 31, 2010 PPD Development L. P. Upon contract execution	Dec. 31, 2010 PPD Development L. P. Upon a clinical study commencement of enrollment in North America	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	Nov. 02, 2012 Novella Clinical, Inc.	Dec. 31, 2012 Novella Clinical, Inc. Upon the achievement of various milestones	Mar. 31, 2014 Novella Clinical, Inc. Upon two database related milestones	Dec. 31, 2013 Novella Clinical, Inc. Upon two database related milestones	Mar. 31, 2014 Intrexon Corporation	Jan. 06, 2011 Intrexon Corporation Quarterly Payment	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	Oct. 17, 2013 New York, NY sqft	Dec. 31, 2013 New York, NY	Dec. 31, 2012 New York, NY sqft	Mar. 31, 2014 New York, NY	Jan. 31, 2012 New York, NY sqft	Dec. 31, 2011 New York, NY sqft	Aug. 30, 2013 Boston, MA sqft	Dec. 31, 2013 Boston, MA	Dec. 31, 2011 Boston, MA	Mar. 31, 2014 Boston, MA sqft	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
Commitments and Contingencies Disclosure [Line Items]
Office space under operating lease																																																																				7,259			6,251				21,184			4,113			9,800
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
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							(641,000)																																																												(392,000)						(194,000)
Operating lease space																																																																													5,249		8,538	6,959
Security deposits																																																																											127,000	127,000					41,000
Security deposit from subtenant																																																																											20,000
Total rent Expense	167,000	289,000					5,400,000
Deferred rent - current portion	224,000	58,000	212,000				224,000
Deferred rent - non-current portion	792,000	384,000	851,000				792,000
Deferred rent liability net	1,000,000	442,000					1,000,000
Number of products																				2
Licensing fee																															125,000								50,000
Stock options, granted	80,500	110,900																				250,487
Option to purchase common stock																						50,222											27,616
Sale of stock price per share																						$ 0.002											$ 0.02
Shares vested																												12,555	25,111				6,904				6,904
Stock based compensation	1,223,000	1,541,000					24,911,000														120,000
Shares expected to vest																														12,556
Milestone payment																								100,000	250,000	100,000	100,000								100,000		300,000	100,000											625,000			4,000,000	1,800,000	1,100,000	3,800,000	9,200,000		256,000	10,000	136,000				2,200,000	7,300,000
Milestone maximum payment																							4,500,000											4,000,000						775,000										8,000,000	20,000,000						790,000						9,500,000
Shares exercised	479,705																															6,904				6,904
Research expenses	6,542,000	19,112,000					261,739,000																																							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
Asset Purchase Agreement, additional cash payment for existing inventory																																																100,000
Annual patent and license prosecution/maintenance fee																																																15,000
Milestones under the license agreement expense	0		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																																																													The Company's 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								45,000	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