Derivatives and Hedging Activities - Impact of Derivative Instruments on AOCI (Details) - Cash flow hedging - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Derivative [Line Items]
Total pre-tax gain/(loss) recognized in AOCI	$ (3,256)	$ 14,757	$ (33,040)	$ (14,021)
Pay fixed/receive floating swaps on borrowings cash flow hedges
Derivative [Line Items]
Pay fixed/receive floating swaps on borrowings cash flow hedges	$ (3,256)	$ 14,757	$ (33,040)	$ (14,021)