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Equity Compensation - Assumption Used to Estimate the Fair Value of Stock-Based Awards (Details)
3 Months Ended
Apr. 30, 2021
Apr. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected dividends (in percentage) 0.00%  
Performance Stock Units    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Range of expected volatilities (in percentage) 36.90% 50.70%
Expected dividends (in percentage) 0.00% 0.00%
Range of risk-free interest rates (in percentage) 0.10% 0.30%
1998 Employee Qualified Stock Purchase Plan    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected dividends (in percentage) 0.00% 0.00%
1998 Employee Qualified Stock Purchase Plan | Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Range of expected volatilities (in percentage) 36.50% 39.40%
Range of expected lives (in years) 6 months 6 months
Range of risk-free interest rates (in percentage) 0.10% 0.30%
1998 Employee Qualified Stock Purchase Plan | Maximum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Range of expected volatilities (in percentage) 41.80% 45.80%
Range of expected lives (in years) 2 years 2 years
Range of risk-free interest rates (in percentage) 0.20% 0.50%