Investment Securities (Narrative) (Details) - USD ($)	3 Months Ended
Aug. 31, 2019	Sep. 01, 2018
Investments, Debt and Equity Securities [Abstract]
Proceeds from sale of available-for-sale securities	$ 69,900,000	$ 53,000,000.0
Gross realized gains on sales of available-for-sale securities	558,000	1,000
Gross realized losses on sales of available-for-sale securities	$ 0	$ 8,000

The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26853-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a),(b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585

Name:	us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration