Consolidated Statements of Comprehensive Income (Loss) (Parentheticals) - USD ($)	12 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Net change in unrealized appreciation of investments, taxes	$ 22,300,000	$ 1,028,000	$ 5,764,000
Reclassification adjustment of other-than-temporary impairment losses recognized in net income, taxes	$ 0	$ 0	$ 146,000

Amount of tax expense (benefit) before reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (e,f)
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration