Note 6 - Investment Securities (Details Textual) - USD ($) $ in Millions	May 27, 2017	Feb. 25, 2017
Auction Rate Securities [Member]
Available-for-sale Securities Temporary Impairment Adjustment Accumulated Other Comprehensive Income (Loss)	$ 0.8	$ (1.0)
Available-for-sale Securities, Long-term Investments, Amortized Cost	20.3	20.3
Other Trading Investment Securities [Member]
Deferred Compensation Plan Assets	$ 76.6	$ 70.3

Carrying amount as of the balance sheet date of assets held under deferred compensation agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_DeferredCompensationPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant