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Share Repurchase Program (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Dec. 17, 2014
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |
Stock repurchase program expiration date | Dec. 31, 2015 |  |  |  |
Stock purchased under repurchase program (in shares) |  |  | 806,018 |  |
Stock purchased under repurchase program, value |  | $ 3,740,000 | $ 25,000,000 | $ 21,259,000 |
Stock purchased under repurchased program, average purchase price per share (in dollars per share) |  |  | $ 31.02 |  |
Maximum |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |
Stock repurchase program, authorized amount |  |  |  |  | $ 25,000,000

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- Definition Number of shares that have been repurchased during the period and are being held in treasury. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 + Details
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