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Related Parties - Additional Information (Details) - USD ($)
3 Months Ended 9 Months Ended
Oct. 31, 2017
Oct. 31, 2016
Oct. 31, 2017
Oct. 31, 2016
Jan. 31, 2017
Related Party Transaction [Line Items]          
Subscription revenue recognized $ 42,795,000 $ 30,799,000 $ 118,223,000 $ 83,954,000  
Outstanding receivables 32,958,000   32,958,000   $ 47,614,000
T. Rowe Associates, Inc.          
Related Party Transaction [Line Items]          
Subscription revenue recognized 171,000 $ 131,000 436,000 $ 378,000  
Outstanding receivables $ 0   $ 0   $ 0