Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Textual) (Details)

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Stockholders' Equity (Textual) (Details) (USD $)
0 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 1 Months Ended 0 Months Ended 12 Months Ended 0 Months Ended 1 Months Ended
Apr. 27, 2010
Dec. 31, 2012
Dec. 31, 2010
Dec. 31, 2011
Dec. 31, 2012
2002 Plan [Member]
Dec. 31, 2012
2010 Plan [Member]
Mar. 31, 2010
2010 Plan [Member]
Dec. 31, 2012
Incentive Stock Options [Member]
Dec. 31, 2012
Restricted stock units [Member]
Dec. 31, 2012
Non-Statutory Stock Options [Member]
Dec. 31, 2012
Stock Options [Member]
Dec. 31, 2011
Stock Options [Member]
Dec. 31, 2010
Stock Options [Member]
Dec. 31, 2010
Redeemable Convertible Preferred Stock [Member]
Aug. 31, 2012
Redeemable Convertible Preferred Stock [Member]
Stockholder Rights Plan [Member]
Dec. 31, 2012
Redeemable Convertible Preferred Stock [Member]
Stockholder Rights Plan [Member]
Apr. 27, 2010
Convertible Preferred Stock [Member]
Dec. 31, 2010
Common Stock [Member]
Dec. 31, 2010
Additional Paid-in Capital [Member]
Apr. 27, 2010
Warrant [Member]
Jul. 31, 2012
Chief Executive Officer [Member]
Restricted Stock [Member]
Jul. 31, 2012
Chief Executive Officer [Member]
Stock Options [Member]
Sep. 30, 2012
Chief Financial Officer [Member]
Restricted Stock [Member]
Sep. 30, 2012
Chief Financial Officer [Member]
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                
Shares reserved for future issuance (shares)         0 10,857,842 1,100,000                                  
Additional shares reserved for future issuance (shares)           1,439,827                                    
Stock option expiration period (in years)   10 years                                            
Option price as a percent of common stock (percent)               100.00%   85.00%                            
Percent of voting interests (percent)                     10.00%                          
Purchase price of common stock when voting percent is above minimum threshold (percent)                     110.00%                          
Vesting period of units granted                 4 years   4 years                   4 years 36 months 4 years 36 months
Annual stock option vesting percentage (percent)                 25.00%   25.00%                   25.00% 25.00% 25.00% 25.00%
Stock units granted (shares)                 1,147,953       20,000               750,000 400,000 50,000 200,000
Exercises, weighted average exercise price per share (dollars per option)                     $ 1.78 $ 2.21     $ 11.35             $ 3.46   $ 2.72
Compensation expense                 $ 1,800,000                              
Stock units released (shares)                 167,401                              
Stock units canceled (shares)                 568,960                              
Outstanding number of shares (shares)                 957,811                              
Weighted average remaining life of stock units (in years)                 2 years 2 months 5 days                              
Outstanding stock units, weighted average grant date fair value (dollars per share)                 $ 3.54                              
Unamortized compensation cost   9,400,000             5,400,000                              
Stock options granted, weighted average grant date fair value (dollars per share)                     $ 1.91 $ 5.19 $ 7.06                      
Options exercisable, weighted average exercise price per share (dollars per share)                     $ 7.21                          
Options exercisable, aggregate intrinsic value                     657,000                          
Stock options exercised, aggregate intrinsic value                     900,000 9,000,000 6,600,000                      
Unrecognized compensation cost, period for recognition (in years)   1 year 10 months 13 days                                            
Shares issued for initial public offering, net of issuance costs (shares) 6,000,000                                 6,000,000            
Stock price per share (dollars per share) $ 13.00                                              
Shares issued for initial public offering, net of issuance costs $ 67,700,000   $ 67,711,000                             $ 1,000 $ 67,710,000          
Conversion of preferred stock to common stock at initial public offering (shares)                           25,199,000     25,307,446 25,307,000   288,438        
Preferred stock dividends (shares)                             1                  
Preferred stock, par value (dollars per share)   $ 0.0001   $ 0.0001                       $ 0.0001                
Ownership percentage threshold under stockholder rights plan (percent)                             15.00%                  
Redemption price (dollars per share)                             $ 0.0001