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Employee Benefit Plans Defined Contribution Benefits (Details) - USD ($)
$ in Millions
12 Months Ended
Jan. 31, 2018
Jan. 31, 2017
Jan. 31, 2016
Defined Contribution Plan Disclosure [Line Items]      
Deferred Compensation Arrangement with Individual, Recorded Liability $ 28.9 $ 26.5  
Profit-sharing feature [Member]      
Defined Contribution Plan Disclosure [Line Items]      
Defined Contribution Plan, Cost 3.9 2.3 $ 0.0
Retirement Savings Feature [Member]      
Defined Contribution Plan Disclosure [Line Items]      
Defined Contribution Plan, Cost $ 8.2 7.5 7.3
Employees contribution percentage 50.00%    
Percentage Of Matching Contribution Made By Company Of First Six Percentage Of Participating Employees Contribution 50.00%    
Percentage Of Participating Employees Contribution Matched By Employer 3.00%    
Employee Profit Sharing and Retirement Savings Plan [Member]      
Defined Contribution Plan Disclosure [Line Items]      
Percent Investment In Company Stock 20.00%    
DCRB Feature of EPSRS Plan [Member]      
Defined Contribution Plan Disclosure [Line Items]      
Defined Contribution Plan, Cost $ 5.2 $ 4.6 $ 3.2