Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Details Textual)

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Stockholders' Equity (Details Textual) (USD $)
9 Months Ended 3 Months Ended 9 Months Ended 1 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Public Offering [Member]
Sep. 30, 2012
April 2013 [Member]
Sep. 30, 2012
Stock Options [Member]
Sep. 30, 2011
Stock Options [Member]
Sep. 30, 2012
Restricted Stock [Member]
Dec. 31, 2011
Restricted Stock [Member]
May 31, 2012
2002 Stock Incentive Plan [Member]
Sep. 30, 2012
2002 Stock Incentive Plan [Member]
Stock Options [Member]
Sep. 30, 2012
Employee Stock Purchase Plan [Member]
Sep. 30, 2011
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period             71,825          
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number             148,330 115,506        
Increase the number of shares under the 2002 Stock Incentive Plan                 1,800,000      
Weighted-average grant date fair value of stock options         $ 14.73              
Intrinsic value of options exercised         $ 300,000 $ 4,000            
Unrecognized compensation cost         6,600,000              
Weighted-average period in which cost is expected to be recognized         2 years 9 months 11 days   1 year 8 months 12 days          
Shares available for future option grants                   1,800,000    
Weighted-average grant-date fair value of restricted stock             $ 13.75          
Unrecognized compensation cost, restricted stock             1,200,000          
Employee Stock Purchase Plan [Abstract]                        
Shares allowed to purchase in employee stock purchase plan                     1,250  
Offering period of shares in employee stock purchase plan                     6 months  
Description of purchase price of stock                     equal to 85% of the lesser of fair market value on either the start date of the period or the last trading day of the period (the “Lookback Provision”).  
Percentage lesser of fair market value taken as purchase price of share                     85.00%  
Common stock issued under amended ESSP                     7,374 2,404
Proceeds Received under amended ESPP                     75,000 18,000
Discount rate                     15.00%  
Stock-based compensation expense 3,116,000 2,646,000                 29,000 700
Shares available for future purchases                     89,917  
Warrants [Abstract]                        
Warrants outstanding       163,568                
Exercise price of warrants       179.40                
Warrants to purchase number of shares       129,360                
Entitled value when warrants exercised       100,000                
Entitled value when warrants exercised, shares       981,411                
Public Offering [Abstract]                        
Stock issued, shares     150,000                  
Stock issued, weighted average price per share     $ 18.19                  
Proceeds from issuance of common stock, net $ 3,181,000 $ 2,000 $ 2,600,000                  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value             $ 12.51 $ 10.63        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period             108,661          
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value             $ 11.48          
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period             4,012          
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value             $ 10.57