Consolidated Statements of Stockholders' Equity (Deficit) (USD $) In Thousands, except Share data, unless otherwise specified	Common stock	APIC	Notes Receivable from Related Parties	Accumulated Deficit	Total
Balance at Dec. 31, 2013	$ 6	$ 275,803	$ (1,069)	$ (162,560)	$ 112,180
Balance (in shares) at Dec. 31, 2013	59,955,343				59,955,343
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss				(24,955)	(24,955)
Issuance of common stock in connection with initial public offering, net of underwriting discounts and offering costs	1	69,150			69,151
Issuance of common stock in connection with initial public offering, net of underwriting discounts and offering costs (in shares)	8,941,250
Conversion of Series A convertible preferred stock in connection with initial public offering		29,224			29,224
Conversion of Series A convertible preferred stock in connection with initial public offering (in shares)	2,857,143
Stock-based compensation		12,154			12,154
Issuance of warrants in connection with marketing agreements		4,668			4,668
Exercise of warrants to purchase common stock	1	9,460			9,461
Exercise of warrants to purchase common stock (in shares)	3,319,540
Exercise of options to purchase common stock		1,760			1,760
Exercise of options to purchase common stock (in shares)	1,741,058
Imputed interest on notes receivable		10			10
Interest income on notes receivable			(3)		(3)
Repayment of notes receivable			1,072		1,072
Balance at Jun. 30, 2014	$ 8	$ 402,229		$ (187,515)	$ 214,722
Balance (in shares) at Jun. 30, 2014	76,814,334				76,814,334