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FHLB Advances and Other Borrowings - Weighted Average Cost and Amount of Advances (Details) - USD ($) $ in Thousands | 12 Months Ended
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Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2015
Federal Home Loan Banks [Abstract] |  |  |
Weighted average interest rate, net of cash flow hedges, at end of year | 2.80% | 3.15% | 3.35%
Weighted daily average interest rate, net of cash flow hedges, during the year | 3.00% | 3.22% | 3.57%
Daily average of FHLB advances during the year | $ 2,167,986 | $ 1,992,434 | $ 1,848,904
Maximum amount of FHLB advances at any month end | 2,350,000 | 2,080,000 | 1,930,000
Interest expense during the year (excludes interest rate swap expense) | $ 64,968 | $ 64,058 | $ 64,331

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- Definition The calculated weighted average interest rate for Federal Home Loan Bank advances outstanding as of the Balance Sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.13(3)(a)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition The calculated weighted average interest rate for Federal Home Loan Bank advances for the period ended as of the Balance Sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.13(3)(a)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition The maximum balance outstanding at any month end during the period as of the Balance Sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.13(3)(a)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition Federal Home Loan Bank, Advances, Activity for Year, Daily Average Balance of Agreements Outstanding + References No definition available. + Details
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