Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2016
Employee Benefit Plans [Abstract]
Maximum percent of gross wages employees may contribute	75.00%
Matching contributions	$ 2.1	$ 1.9	$ 1.9
Value of shares of common stock owned by remaining plan participants in deferred compensation plan	$ 0.2	$ 0.4

Value of common stock issued to a trust (for example, a 'rabbi trust') set up specifically to accumulate stock for the sole purpose of distribution to participating employees. This trust does not allow employees to immediately or after a holding period diversify into nonemployer securities. The deferred compensation plan for which this trust is set up must be settled by the delivery of a fixed number of shares of employer stock.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 25
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=75028277&loc=d3e19833-108362

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