Fair Value Measurements - Reconciliation of Company's Liabilities Measured Using Significant Unobservable Inputs (Detail) (USD $)	3 Months Ended		9 Months Ended		80 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2013 Significant Unobservable Inputs (Level 3) [Member] Preferred stock warrant liability [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Preferred stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance						$ 56,000	$ 39,000
Warrants issued in connection with loan and security agreement						49,000	24,250
Change in fair value of warrant liability	39,000	1,550	(82,000)	4,550	(54,264)	82,000	(7,250)
Reclassification to additional paid-in capital upon closing of IPO						(187,000)
Ending balance							$ 56,000