Consolidated Statements of Stockholders' Equity (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
Net loss				(38,595)	(38,595)
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		21,925			21,925
Issuance of warrants in connection with marketing agreements		8,343			8,343
Exercise of warrants to purchase common stock	1	9,460			9,461
Exercise of warrants to purchase common stock (in shares)	3,348,095
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes		1,909			1,909
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes (in shares)	1,881,170
Imputed interest on notes receivable		10			10
Interest income on notes receivable			(3)		(3)
Repayment of notes receivable			1,072		1,072
Balance at Sep. 30, 2014	$ 8	$ 415,824		$ (201,155)	$ 214,677
Balance (in shares) at Sep. 30, 2014	76,983,001				76,983,001