Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended	6 Months Ended	12 Months Ended	67 Months Ended	1 Months Ended		1 Months Ended		6 Months Ended
	Mar. 06, 2014	Mar. 31, 2014	Jun. 30, 2014 Segment	Dec. 31, 2013	Jun. 30, 2014	Mar. 31, 2014 Remeasurement [Member]	Mar. 31, 2014 IPO [Member]	Feb. 28, 2014 Series D convertible preferred stock [Member]	Feb. 28, 2014 Series E convertible preferred stock [Member]	Jun. 30, 2014 Minimum [Member]	Jun. 30, 2014 Maximum [Member]
Significant Accounting Policies [Line Items]
Number of operating segment			1
Reverse stock split	1-for-11.5
Cash and cash equivalents maturity period			Three months or less
Cash and cash equivalents of restricted cash held for credit cards			$ 100,000	$ 100,000	$ 100,000
Property and equipment estimated useful lives										3 years	5 years
Impairments of long-lived assets			0	0	0
Inception date			Dec. 10, 2008
Warrants exercised, shares		158,179
Remeasured of outstanding warrants		173,910
Warrants remeasured using intrinsic value of warrant computed as difference between IPO price and exercise price		$ 5.17					$ 21.00
Expense related to change in fair value						2,300,000
Reclassified to additional paid in capital						2,800,000
Remeasurement of preferred stock								9,600,000
Convertible preferred stock shares automatically converted into common stock		15,876,104							48,758,857
Convertible preferred stock, Purchase price									$ 1.128
Purchase price of convertible preferred stock									55,000,000
Number of common stock automatically converted from convertible preferred stock upon completion of the Company's IPO									4,239,984
Deemed dividend			$ 25,559,000		$ 25,559,000				$ 25,600,000
Percentage for the amount of benefit realized upon ultimate settlement											50.00%