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Employee Benefit Plans | Retirement Savings Plan (Details) - Retirement Savings Plan [Member] - USD ($)
$ in Millions
12 Months Ended
Jan. 31, 2020
Jan. 31, 2019
Jan. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Deferred Compensation Arrangement With Individual, Employer Matching Contribution, Percentage 50.00%    
Deferred Compensation Arrangement With Individual Maximum Employer Matching Of Participant Deferrals, Percentage 6.00%    
Deferred Compensation Arrangement with Individual, Requisite Service Period 4 years    
Deferred Compensation Arrangement with Individual, Contributions by Employer $ 7.1 $ 6.7 $ 6.4