Commitments and Contingencies (Details) (USD $)
3 Months Ended 9 Months Ended
Oct. 31, 2012
Oct. 31, 2011
Oct. 31, 2012
Oct. 31, 2011
Nov. 20, 2012
Nov. 16, 2012
Commitments and Contingencies            
Rent expense $ 900,000 $ 800,000 $ 2,600,000 $ 1,800,000    
Operating lease obligations            
Total         45,585,000  
Future minimum payments pertaining to an amendment         30,600,000  
Less Than 1 year         3,325,000  
1-3 years         13,442,000  
3-5 years         14,977,000  
More Than 5 years         13,841,000  
Future sublease rental income           $ 2,800,000