Statement of Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Junior Series A Preferred Stock	Common stock.	Additional paid-in capital	Accumulated Deficit.	Accumulated Other Comprehensive Loss	Total
Balance at Dec. 31, 2012	$ 3,000	$ 1		$ (126,471)		$ (123,470)
Balance (in shares) at Dec. 31, 2012	3,000	1,470
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon conversion of Series A, A-1, B, B-1, and C preferred stock		$ 21	$ 174,310			174,331
Issuance of common stock upon conversion of Series A, A-1, B, B-1, and C preferred stock (in shares)		21,038
Issuance of common stock from initial public offering, net		$ 9	175,546			175,555
Issuance of common stock from initial public offering, net (in shares)		8,740
Issuance of common stock upon conversion of Junior Series A Preferred Stock	$ (3,000)					(3,000)
Issuance of common stock upon conversion of Junior Series A Preferred Stock (in shares)	(3,000)
Reclassification of warrant liability			2,179			2,179
Reclassification of preferred stock issuance costs			(1,804)			(1,804)
Issuance of common stock under employee stock compensation plans and warrants			94			94
Issuance of common stock under employee stock compensation plans and warrants (in shares)		165
Share-based compensation			2,871			2,871
Preferred Stock dividends			(457)	(5,434)		(5,891)
Net loss				(51,145)		(51,145)
Balance at Dec. 31, 2013		$ 31	352,739	(183,050)		169,720
Balance (in shares) at Dec. 31, 2013		31,413
Increase (Decrease) in Stockholders' Equity
Issuance of common stock from follow-on public offering, net		$ 2	55,407			55,409
Issuance of common stock from follow-on public offering, net (in shares)		1,900
Issuance of common stock under employee stock compensation plans and warrants		$ 1	2,948			2,949
Issuance of common stock under employee stock compensation plans and warrants (in shares)		682
Share-based compensation			13,040			13,040
Excess tax benefit from share-based compensation			4,256			4,256
Net loss				(116,772)		(116,772)
Unrealized loss on available for sale securities, net of tax					$ (65)	(65)
Balance at Dec. 31, 2014		$ 34	428,390	(299,822)	(65)	128,537
Balance (in shares) at Dec. 31, 2014		33,995
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under employee stock compensation plans and warrants		$ 1	11,472			11,473
Issuance of common stock under employee stock compensation plans and warrants (in shares)		1,202
Share-based compensation			24,760			24,760
Excess tax benefit from share-based compensation			1,302			1,302
Net loss				(105,717)		(105,717)
Unrealized loss on available for sale securities, net of tax					(408)	(408)
Balance at Dec. 31, 2015		$ 35	$ 465,924	$ (405,539)	$ (473)	$ 59,947
Balance (in shares) at Dec. 31, 2015		35,197