Note 5 - Fair Value Measures (Details Textual) - USD ($) $ in Thousands	Feb. 28, 2019	Aug. 31, 2018	Aug. 31, 2017
Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure	$ 0	$ 0
Financial Liabilities Fair Value Disclosure, Total	0	$ 0
Fair Value, Inputs, Level 2 [Member] \| Estimate of Fair Value Measurement [Member]
Long-term Debt, Fair Value	$ 575,000		$ 575,000

Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant