Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $) In Thousands, except Share data	Total	Series D Preferred Stock	Series 1 Preferred Stock	IPO	Follow-on Offering	Convertible Preferred Stock	Convertible Preferred Stock Series D Preferred Stock	Convertible Preferred Stock Series 1 Preferred Stock	Common Stock	Common Stock IPO	Common Stock Follow-on Offering	Additional Paid-in Capital	Additional Paid-in Capital Series D Preferred Stock	Additional Paid-in Capital Series 1 Preferred Stock	Additional Paid-in Capital IPO	Additional Paid-in Capital Follow-on Offering	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance at beginning of year at Dec. 31, 2010	$ (228,407)					$ 220,374			$ 1			$ 5,266					$ (233,670)	$ (4)
Balance at beginning of year (in shares) at Dec. 31, 2010						17,103,729			1,224,782
Exercise of employee stock options for cash (in shares)									51,336
Exercise of employee stock options for cash	149											149
Lapse of repurchase rights related to common shares issued pursuant to early exercises (in shares)									3.614
Lapse of repurchase rights related to common shares issued pursuant to early exercises	19											19
Issuance of stock (in shares)							6,287,026	636,042
Issuance of stock		(115)	(91)				88,962	7,944					(115)	(91)
Employee stock-based compensation expense	2,288											2,288
Compensation expense relating to stock options granted to consultants	65											65
Unrealized gain on available-for-sale securities, net of tax	3																	3
Net income (loss)	19,984																19,984
Balance at end of the year at Dec. 31, 2011	(206,105)					317,280			1			7,581					(213,686)	(1)
Balance at end of the year (in shares) at Dec. 31, 2011						24,026,797			1,279,732
Exercise of employee stock options for cash (in shares)									104,417
Exercise of employee stock options for cash	317											317
Lapse of repurchase rights related to common shares issued pursuant to early exercises (in shares)									1,359
Lapse of repurchase rights related to common shares issued pursuant to early exercises	10											10
Employee stock-based compensation expense	2,665											2,665
Compensation expense relating to stock options granted to consultants	144											144
Unrealized gain on available-for-sale securities, net of tax	34																	34
Net income (loss)	11,366											10,717					11,366
Balance at end of the year at Dec. 31, 2012	(191,569)					317,280			1								(202,320)	33
Balance at end of the year (in shares) at Dec. 31, 2012						24,026,797			1,385,508
Exercise of employee stock options for cash (in shares)	403,468								403,468
Exercise of employee stock options for cash	2,529											2,529
Lapse of repurchase rights related to common shares issued pursuant to early exercises (in shares)									500
Lapse of repurchase rights related to common shares issued pursuant to early exercises	4											4
Issuance of stock (in shares)										9,686,171	5,412,686
Issuance of stock				125,872	119,975					11	5				125,861	119,970
Employee stock-based compensation expense	4,140											4,140
Compensation expense relating to stock options granted to consultants	775											775
Unrealized gain on available-for-sale securities, net of tax	22																	22
Net income (loss)	(83,352)																(83,352)
Conversion of preferred stock warrants to common stock warrants	659											659
Conversion of preferred stock to common stock (in shares)						(24,026,797)			24,026,797
Conversion of preferred stock to common stock	317,280					(317,280)			24			317,256
Balance at end of the year at Dec. 31, 2013	$ 296,335								$ 41			$ 581,911					$ (285,672)	$ 55
Balance at end of the year (in shares) at Dec. 31, 2013						0			40,915,130