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Derivatives and Hedging Activities - Impact of Derivative Instruments on AOCI (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
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Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019
Derivative [Line Items] |  |  |  |
Total pre-tax gain/(loss) recognized in AOCI | $ (8,045) | $ (10,043) | $ (17,358) | $ (26,692)
Pay fixed/receive floating swaps on borrowings cash flow hedges |  |  |  |
Derivative [Line Items] |  |  |  |
Total pre-tax gain/(loss) recognized in AOCI | $ (8,045) | $ (10,043) | $ (17,358) | $ (26,692)

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- Definition Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 20 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=121577181&loc=SL110061190-113977 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e637-108580 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669646-108580 + Details
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