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Customer Accounts - Interest Expense on Customer Accounts (Details) - USD ($) $ in Thousands | 12 Months Ended
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Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2015
Banking and Thrift [Abstract] |  |  |
Checking accounts | $ 2,721 | $ 1,491 | $ 1,036
Savings accounts | 978 | 734 | 660
Money market accounts | 3,592 | 3,285 | 3,631
Time deposit accounts | 45,256 | 47,425 | 46,273
Interest expense on customer accounts, gross | 52,547 | 52,935 | 51,600
Less early withdrawal penalties | (524) | (450) | (546)
Interest expense on customer accounts | $ 52,023 | $ 52,485 | $ 51,054
Weighted average interest rate at end of year | 0.54% | 0.50% | 0.48%
Weighted daily average interest rate during the year | 0.49% | 0.50% | 0.48%

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- Definition The interest expense recognized during the period on customer deposits or security deposits held in interest bearing accounts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.8) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
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- Definition Interest expense incurred on demand deposit accounts that represent borrowings rather than outstanding drafts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.6) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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- Definition Aggregate amount of interest expense on all deposits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.6) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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- Definition Early withdrawal penalties on domestic deposits which discourage customer withdrawal prior to maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.6) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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- Definition Interest expense incurred on all money market deposits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.6) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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- Definition Interest expense incurred on all savings account deposits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.6) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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- Definition The aggregate interest expense incurred on time deposits, including certificates of deposits, in domestic offices. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.6) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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- Definition Weighted average interest rate calculated at point in time for domestic deposit liability. + References No definition available. + Details
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- Definition Weighted Average Daily Rate Domestic Deposits + References No definition available. + Details
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