Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended	121 Months Ended	12 Months Ended			1 Months Ended	9 Months Ended	12 Months Ended			1 Months Ended			12 Months Ended			12 Months Ended					12 Months Ended			12 Months Ended		1 Months Ended		9 Months Ended	24 Months Ended		12 Months Ended	1 Months Ended		12 Months Ended	9 Months Ended	1 Months Ended	12 Months Ended					9 Months Ended	12 Months Ended					9 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012 Solasia	Dec. 31, 2012 Solasia Development-based milestones	Dec. 31, 2012 Solasia Sales-based milestones	Jun. 27, 2013 Harmon Hill LLC Collaboration Agreement	Sep. 30, 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	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	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	Sep. 30, 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, 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	Sep. 30, 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, 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	Sep. 30, 2013 Southern Research Institute	Dec. 21, 2006 Southern Research Institute Execution Agreement	Dec. 21, 2006 Southern Research Institute Maximum	Dec. 31, 2012 Intrexon Corporation	Jan. 06, 2011 Intrexon Corporation Quarterly Payment	Nov. 02, 2012 Novella Clinical, Inc.	Dec. 31, 2012 Novella Clinical, Inc. Upon the achievement of various milestones	Sep. 30, 2013 Novella Clinical, Inc. Upon two database related milestones	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.	Sep. 30, 2013 PPD Development L. P. Upon the achievement of various milestones	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, 2011 PPD Development L. P. Upon initial clinical study enrollment	Dec. 13, 2011 Pharmaceutical Research Associates Inc	Sep. 30, 2013 Pharmaceutical Research Associates Inc Upon the achievement of various milestones	Dec. 31, 2012 Pharmaceutical Research Associates Inc Upon the achievement of various milestones
Commitments and Contingencies Disclosure [Line Items]
Licensing fee																										$ 125,000						$ 50,000
Shares of common stock granted	125,000	76,300	1,551,400	508,700															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 expenses	809,000	1,191,000	2,482,000	3,482,000		22,663,000												120,000
Shares expected to vest																									12,556
Milestone payment																					100,000	250,000							100,000	300,000	100,000								256,000	136,000		625,000					9,200,000	1,800,000	1,100,000	3,800,000	4,000,000		2,200,000	7,300,000
Milestone maximum payment																				4,500,000								4,000,000					775,000					790,000							8,000,000	20,000,000						9,500,000
Research expenses	6,247,000	16,215,000	40,133,000	48,464,000		252,478,000																												25,000	200,000
Royalty payment																																	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			0		250,000
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											90,000	200,000	240,000	240,000
Payment for consulting services fee															500,000	15,000	20,000
Agreement period										1 year
Upfront payment received							5,000,000
Expected Additional milestone payments to be received								$ 32,500,000	$ 53,500,000