Commitments and Contingencies - Additional Information (Detail) (USD $)	0 Months Ended				1 Months Ended
	Aug. 06, 2014 LegalMatter	Mar. 29, 2013	Oct. 12, 2012	May 02, 2012	Jul. 31, 2014	Feb. 28, 2009	Sep. 30, 2014	Dec. 31, 2013	Aug. 01, 2013
Commitment And Contingencies [Line Items]
Severance payment due to Dr. Platt						$ 1,000,000		$ 1,000,000
Number of options vested						83,334
Equity investment							10,000
Royalty revenue						50,000,000
Market capitalization						100,000,000			100,000,000
Severance payment period						6 months
Separation based payments				1,000,000
Lawsuit payment			1,000,000
Milestone payments		1,000,000
Expected future payment									1,000,000
Payment of severance obligation					1,000,000
Number of putative class action complaints filed	3
Minimum
Commitment And Contingencies [Line Items]
Cashless stock option exercisable period						10 years
Equity investment						$ 10,000,000
Cashless stock option exercisable						50,000