Equity Incentive Plans - Stock Grants (Details) - shares	12 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Board of Director Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	43,519	86,082	69,281
Board of Director Units, Compensation Related Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	28,065	55,380	49,267
Award vesting period (in years)	1 year
Board of Director Units, Deferred Annual Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	13,065	25,560	13,318
Award vesting period (in years)	1 year
Board of Director Units, Deferred Quarterly Dividends
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	2,389	5,142	6,876
Award vesting period (in years)	1 year

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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