Property and Equipment (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 9 Months Ended
Oct. 31, 2012
Oct. 31, 2011
Oct. 31, 2012
Oct. 31, 2011
Jan. 31, 2012
Property and Equipment          
Property and equipment, gross $ 19,775   $ 19,775   $ 14,579
Less: accumulated depreciation and amortization (9,017)   (9,017)   (5,660)
Property and equipment, net 10,758   10,758   8,919
Depreciation and amortization expense 1,200 600 3,357 1,429  
Computer equipment and software
         
Property and Equipment          
Property and equipment, gross 15,454   15,454   10,712
Furniture and fixtures
         
Property and Equipment          
Property and equipment, gross 2,652   2,652   1,964
Leasehold improvements
         
Property and Equipment          
Property and equipment, gross $ 1,669   $ 1,669   $ 1,903