Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Details Textual)

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Stockholders' Equity (Details Textual) (USD $)
 1 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended
Mar. 31, 2012
Jan. 31, 2013
Jan. 31, 2012
Jan. 31, 2011
Jul. 31, 2008
Employee Stock [Member]
Jan. 31, 2011
Employee Stock [Member]
Jan. 31, 2013
Employees [Member]
Jan. 31, 2012
Employees [Member]
Jan. 31, 2011
Employees [Member]
Jan. 31, 2011
Compensation and Incentive Plan 2011 [Member]
May 31, 2012
Compensation and Incentive Plan 2011 [Member]
Executive Officer [Member]
Jan. 31, 2013
Amended and Restated Equity Compensation and Incentive Plan 2005 [Member]
Jan. 31, 2013
Restricted Stock Units (Rsus) [Member]
Jan. 31, 2011
Restricted Stock Units (Rsus) [Member]
Jan. 31, 2013
Restricted Stock Units (Rsus) [Member]
Executive Officer [Member]
Performance Based Plan [Member]
Preferred Stock, Shares Authorized   5,000,000                          
Stock Issued During Period, Shares, New Issues                   2,800,000   2,800,000      
Stock Repurchase Program, Authorized Amount $ 25,000,000                            
Stock Repurchase Program Shares Authorized To Repurchase Par Value $ 0.01                            
Stock Repurchased During Period, Shares (in shares)   764,024                          
Stock Repurchase Price Per Share (in dollars per share)   $ 8.12                          
Stock Repurchased During Period, Value   6,200,000                          
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant   857,515                          
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent       100.00%                      
Share Based Compensation Arrangement By Share Based Payment Award, Vesting Period Description                   Awards granted under the 2011 Plan generally vest over three years and expire 10 years from the date of the grant          
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value   $ 3.78 $ 2.86 $ 3.70                      
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized   2,300,000                     3,900,000    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value   500,000 800,000 500,000                      
Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options           700,000 2,200,000 1,800,000 2,100,000            
Share Based Compensation Arrangement By Share Based Payment Award Estimated Weighted Average Amortization Period                         2 years 1 month 6 days    
Share Based Compensation Arrangement By Share Based Payment Award Unvested Stock Cancelled In Period Grant Date Fair Value                           1,900,000  
Stock-based compensation expense   $ 4,101,000 $ 2,988,000 $ 2,598,000                   $ 1,300,000  
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares Per Employee         2,200,000                    
Share Based Compensation Arrangement By Share Based Payment Award, Purchase Price Description         The purchase price of the stock was 85% of the lesser of the average market price of the common stock on the first or last business day of each six-month plan period.                    
Issuance of common stock in connection with the employee stock purchase plan (in shares)           135,632                  
Shares, Granted   892,500 250,000 15,000             875,000       90,673