Collaboration Agreements - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended				9 Months Ended	12 Months Ended	1 Months Ended	3 Months Ended	9 Months Ended		0 Months Ended		1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended				1 Months Ended	9 Months Ended
	Jul. 29, 2013	May 31, 2014	Dec. 31, 2013	Oct. 31, 2011	Apr. 30, 2010	Sep. 30, 2014 Licensed_Program Candidate	Dec. 31, 2013	Jul. 31, 2014 Celgene [Member]	Sep. 30, 2013 Celgene [Member]	Sep. 30, 2014 Celgene [Member]	Sep. 30, 2013 Celgene [Member]	Jul. 31, 2014 Celgene [Member] Split License [Member]	Jan. 01, 2014 Celgene [Member] In Process Research and Development [Member]	Jul. 31, 2014 Celgene [Member] In Process Research and Development [Member]	Sep. 30, 2014 Celgene [Member] In Process Research and Development [Member]	Jul. 31, 2014 Celgene [Member] Participation Service [Member]	Sep. 30, 2014 Celgene [Member] MTD [Member]	Sep. 30, 2014 Celgene [Member] Before Amendment [Member]	Sep. 30, 2014 Celgene [Member] Before Amendment [Member]	Sep. 30, 2014 Maximum [Member]	Dec. 31, 2013 Maximum [Member]	Sep. 30, 2014 Minimum [Member]	Jul. 31, 2013 Series B Convertible Preferred Stock [Member]	Sep. 30, 2014 Series B Convertible Preferred Stock [Member]	Sep. 30, 2014 Series B Convertible Preferred Stock [Member] Celgene [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Agreement amended date					2011-10
Amended collaboration expiration date			2015-04		2014-04		2015-04
Discovery phase years					2 years
Term of the initial discovery period before amendment to extend			4 years	3 years			4 years
Term of extended period after amendment of the initial discovery period			5 years	4 years			5 years
Eligible payment to be received from extension of the discovery phase						$ 20,000,000															$ 20,000,000
Date of extension of discovery phase			2016-04			2016-04
Number of candidates confirmed by the Joint Research Committee						2
Number of licensed programs type under collaboration agreements						3
Period considered for agreement termination notice						30 days
Upfront payment received						121,200,000
Series B convertible preferred stock, purchased			0			0	0																		5,190,551
Series B convertible preferred stock price per share																								$ 1.70
Net proceeds of Series B convertible preferred stock																								8,800,000
Additional consideration under agreement																								3,100,000
Series B convertible preferred stock at fair value																								5,700,000
Reverse stock split						1-for-2.75																		1-for-2.75
Reverse stock split ratio						0.3636																		0.3636
Additional outstanding shares common stock	19,731,564																						1,887,473
Payment made in pursuant to the amendment		20,000,000		20,000,000
Milestone payment upon achievement of a specified clinical development milestone event								10,000,000		10,000,000										25,000,000		10,000,000
Milestone payment reimbursement, percentage								50.00%		50.00%
Number of years company expected to fulfill its performance obligations																			6 years
Revenue recognition, selling price												21,200,000	42,700,000	13,600,000	50,800,000	200,000
Revenue recognized during period										8,000,000
Collaboration revenue									6,300,000		18,800,000							50,700,000	33,900,000
Receipts of potential milestone payments																				120,000,000
Milestone payments upon achievement of specified regulatory milestone events																				70,000,000
Milestone payment upon achievement of a specified commercial milestone event																				25,000,000
Achievement of an early clinical development milestone event						22,500,000
Dosing of the last patient in a Company-sponsored						25,000,000
Received amount of development cost																	5,000,000
Collaboration receivable						18,700,000
Milestone or royalty payments received										$ 0