Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Common stock	APIC	Notes Receivable from Related Parties	Accumulated Deficit	Accumulated Other Comprehensive Loss	Total
Balance at Dec. 31, 2011	$ 6	$ 223,065	$ (1,258)	$ (63,009)	$ (35)	$ 158,769
Balance (in shares) at Dec. 31, 2011	55,661,539
Increase (Decrease) in Stockholders' Equity
Net loss				(74,495)		(74,495)
Other comprehensive loss, net of tax					35	35
Stock-based compensation		9,658				9,658
Issuance of warrants in connection with marketing agreements		1,990				1,990
Issuance of restricted stock		876				876
Issuance of restricted stock (in shares)	17,520
Exercise of options to purchase common stock		370	(57)			313
Exercise of options to purchase common stock (in shares)	401,494
Imputed interest on notes receivable		126				126
Repurchase of common stock		(1,648)				(1,648)
Repurchase of common stock (in shares)	(265,274)
Issuance of common stock, net of issuance costs		1,329	15			1,344
Issuance of common stock, net of issuance costs (in shares)	140,890
Interest income on notes receivable			(27)			(27)
Beneficial conversion feature related to convertible notes payable, net of tax		1,618				1,618
Issuance and adjustment of contingently redeemable common stock		(1,000)				(1,000)
Issuance and adjustment of contingently redeemable common stock (in shares)	(126,262)
Exercise of warrants to purchase common stock		637				637
Exercise of warrants to purchase common stock (in shares)	377,672
Balance at Dec. 31, 2012	6	237,021	(1,327)	(137,504)		98,196
Balance (in shares) at Dec. 31, 2012	56,207,579
Increase (Decrease) in Stockholders' Equity
Net loss				(25,056)		(25,056)
Stock-based compensation		9,463				9,463
Issuance of warrants in connection with marketing agreements		3,740				3,740
Issuance of restricted stock		423				423
Issuance of restricted stock (in shares)	20,874
Exercise of options to purchase common stock		171	58			229
Exercise of options to purchase common stock (in shares)	98,878
Imputed interest on notes receivable		127				127
Issuance of common stock, net of issuance costs		326				326
Issuance of common stock, net of issuance costs (in shares)	57,760
Interest income on notes receivable			(28)			(28)
Issuance and adjustment of contingently redeemable common stock (in shares)	13,840
Repurchase of vested common stock awards		(2,000)				(2,000)
Repayment of notes receivable			228			228
Issuance of warrants in connection with Series A convertible preferred stock		677				677
Issuance of warrants in connection with revolving line of credit		408				408
Conversion of convertible note payable to common stock		25,447				25,447
Conversion of convertible note payable to common stock (in shares)	3,556,412
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				(48,429)		(48,429)
Stock-based compensation		30,582				30,582
Issuance of warrants in connection with marketing agreements		9,861				9,861
Recovery of short swing profits		14				14
Imputed interest on notes receivable		10				10
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
Issuance of common stock in follow-on offering, net of underwriting discounts and offering costs		30,762				30,762
Issuance of common stock in follow-on offering, net of underwriting discounts and offering costs (in shares)	1,960,390
Interest income on notes receivable			(3)			(3)
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
Exercise of warrants to purchase common stock	1	9,460				9,461
Exercise of warrants to purchase common stock (in shares)	3,357,867
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes		5,313				5,313
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes (in shares)	2,739,776
Repayment of notes receivable			1,072			1,072
Balance at Dec. 31, 2014	$ 8	$ 460,179		$ (210,989)		$ 249,198
Balance (in shares) at Dec. 31, 2014	79,811,769					79,811,769