Consolidated Statements of Convertible Preferred Stock And Stockholders’ Equity - USD ($) $ in Thousands	Convertible preferred stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (loss)	Accumulated Deficit	Total
Balances at Dec. 31, 2012	$ 19,149
Balances (in shares) at Dec. 31, 2012	4,719,174
Balances at Dec. 31, 2013	$ 19,149
Balances (in shares) at Dec. 31, 2013	4,719,174
Balances at Dec. 31, 2012		$ 14	$ 76,447		$ (71,493)	$ 4,968
Balances (shares) at Dec. 31, 2012		9,499,862
Increase (decrease) in shareholders' equity
Exercise of stock options			16			16
Exercise of stock options (shares)		15,666
Vesting of common stock			8			8
Modification of common stock purchase warrants			52			52
Stock-based compensation			640			640
Net income					50,921	50,921
Balances at Dec. 31, 2013		$ 14	77,163		(20,572)	$ 56,605
Balances (shares) at Dec. 31, 2013		9,515,528
Increase (decrease) in temporary equity
Issuance of Series AA preferred stock from the exercise of preferred stock warrants	$ 8,747
Issuance of Series AA preferred stock from the exercise of preferred stock warrants (shares)	622,660
Conversion of preferred stock to common stock in April 2014 in connection with the IPO	$ (27,896)
Conversion of preferred stock to common stock in April 2014 in connection with the IPO (shares)	(5,341,834)
Balances at Dec. 31, 2014
Balances (in shares) at Dec. 31, 2014						0
Increase (decrease) in shareholders' equity
Exercise of stock options		$ 1	480			$ 481
Exercise of stock options (shares)		738,539
Excess tax benefit of stock option exercises			1,599			1,599
Exercise of common stock warrants			453			453
Exercise of common stock warrants (shares)		199,837
Conversion of preferred stock to common stock in April 2014 in connection with the IPO		$ 4	27,892			27,896
Conversion of preferred stock to common stock in April 2014 in connection with the IPO (shares)		4,003,225
Issuance of common stock in initial public offering (“IPO”), net of discounts, commissions and issuance costs		$ 3	42,629			42,632
Issuance of common stock in initial public offering (“IPO”), net of discounts, commissions and issuance costs (Shares)		3,081,371
Net unrealized (loss) gain on available-for-sale securities				$ (180)		(180)
Stock issued under employee stock purchase plan			162			162
Stock issued under employee stock purchase plan (in shares)		12,875
Stock-based compensation			7,203			7,203
Net income					10,223	10,223
Balances at Dec. 31, 2014		$ 22	157,581	(180)	(10,349)	$ 147,074
Balances (shares) at Dec. 31, 2014		17,551,375
Balances at Dec. 31, 2015
Balances (in shares) at Dec. 31, 2015						0
Increase (decrease) in shareholders' equity
Exercise of stock options			761			$ 761
Exercise of stock options (shares)		409,683
Vesting of common stock			112			112
Issuance of common stock in conjunction with Controlled Equity Offering, net of commissions and issuance costs		$ 1	9,656			9,657
Issuance of common stock in conjunction with Controlled Equity Offering, net of commissions and issuance costs(shares)		509,741
Issuance of common stock in conjunction with warrant exercises (in shares)		3,484
Net unrealized (loss) gain on available-for-sale securities				22		22
Stock issued under employee stock purchase plan			407			407
Stock issued under employee stock purchase plan (in shares)		31,179
Stock-based compensation			9,956			9,956
Net income					(51,802)	(51,802)
Balances at Dec. 31, 2015		$ 23	$ 178,473	$ (158)	$ (62,151)	$ 116,187
Balances (shares) at Dec. 31, 2015		18,505,462