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Fair Value Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Feb. 28, 2020
Feb. 22, 2019
Feb. 23, 2018
May 24, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Unrealized gain (loss) on investments $ (0.1) $ 0.4 $ 0.0  
Managed Investment Portfolio and Other Investments [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Available-for-sale Securities, Amortized Cost Basis   0.0   $ 0.0
Unrealized gain (loss) on investments 0.0      
Auction Rate Securities [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Unrealized gain (loss) on investments 0.2      
Available-for-sale Securities, Par Value 3.2      
Other than Temporary Impairment Losses, Investments 0.9      
Available-for-Sale Securities, Maturities [Abstract]        
Estimated Reduction in Fair Value due to a One Hundred Basis Point Increase in Discount Rate 0.3      
Fair Value, Recurring [Member] | Auction Rate Securities [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Available-for-sale Securities, Fair Value Disclosure 2.1 3.9    
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Auction Rate Securities [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Available-for-sale Securities, Fair Value Disclosure $ 2.1 $ 3.9 $ 3.5