Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent	$ 259,649	$ 203,849	$ 170,211	$ (44,743)
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net	26,594	18,701	8,451
Stock Issued During Period, Value, Stock Options Exercised	7,632	7,236	630
Stock Issued During Period, Value, Employee Stock Purchase Plan	4,296	3,860
Vesting of early exercised stock options	0	35	113
Stock Repurchased During Period, Value		0	0
Issuance of Series G redeemable convertible preferred stock, net of issuance cost			0
Preferred Stock, Shares Issued From Exercise Of Stock Warrants, Value			0
Stock Issued During Period, Value, New Issues			93,999
Stock Issued During Period, Value, Conversion of Convertible Securities			77,729
Issuance of preferred stock upon exercise of warrant, Value			2,303
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	9,183	2,019	25
Other Comprehensive Income (Loss), Net of Tax	(95)	(2)
Net Income (Loss) Attributable to Parent	8,190	1,789	31,704
Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Outstanding	0	0	0	43,285,000
Stockholders' Equity Attributable to Parent	0	0	0	51,257
Issuance Of Redeemable Convertible Preferred Stock, Net Of Issuance Cost, Shares			4,590,000
Issuance of Series G redeemable convertible preferred stock, net of issuance cost			24,883
Stock Issued During Period, Shares, Conversion of Convertible Securities			(47,981,000)
Stock Issued During Period, Value, Conversion of Convertible Securities			(77,729)
Preferred Stock [Member] | Warrant [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred Stock, Shares Issued From Exercise Of Stock Warrants			106,000
Preferred Stock, Shares Issued From Exercise Of Stock Warrants, Value			1,589
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Outstanding	85,110,000	80,691,000	74,166,000	18,273,000
Stockholders' Equity Attributable to Parent	85	81	74	18
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	3,618,000	5,903,000	812,000
Stock Issued During Period, Value, Stock Options Exercised	4	6	1
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	319,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans	482,000	345,000
Stock Issued During Period, Value, Employee Stock Purchase Plan		1
Stock Repurchased During Period, Shares		(1,000)	(2,000)
Stock Issued During Period, Shares, New Issues			7,000,000
Stock Issued During Period, Value, New Issues			7
Stock Issued During Period, Shares, Conversion of Convertible Securities			47,981,000
Stock Issued During Period, Value, Conversion of Convertible Securities			48
Common Stock [Member] | Warrant [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Shares Issued From Exercise Of Stock Warrants		278,000	102,000
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent	273,276	225,575	193,731	10,537
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net	26,594	18,701	8,451
Stock Issued During Period, Value, Stock Options Exercised	7,628	7,230	629
Stock Issued During Period, Value, Employee Stock Purchase Plan	4,296	3,859
Vesting of early exercised stock options		35	113
Stock Issued During Period, Value, New Issues			93,992
Stock Issued During Period, Value, Conversion of Convertible Securities			77,681
Issuance of preferred stock upon exercise of warrant, Value			2,303
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	9,183	2,019	25
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent	(97)	(2)	0	0
Other Comprehensive Income (Loss), Net of Tax	(95)	(2)
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent	(13,615)	(21,805)	(23,594)	(55,298)
Net Income (Loss) Attributable to Parent	$ 8,190	$ 1,789	$ 31,704