Fair Value Reconciliation of Changes in Level 3 Balances (Details) - USD ($) $ in Millions	12 Months Ended
	Feb. 28, 2020	Feb. 22, 2019	Feb. 23, 2018	May 24, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gain (loss) on investments	$ (0.1)	$ 0.4	$ 0.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0.0
Managed Investment Portfolio and Other Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gain (loss) on investments	0.0
Available-for-sale Securities, Amortized Cost Basis		0.0		$ 0.0
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gain (loss) on investments	0.2
Fair Value, Recurring [Member] | Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Balance, Beginning of Period	3.9
Fair Value Balance, End of Period	2.1	3.9
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Balance, Beginning of Period	3.9	3.5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(0.1)	0.4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0.5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(2.2)
Fair Value Balance, End of Period	$ 2.1	$ 3.9	$ 3.5