Derivatives and Hedging Activities - Impact of Derivative Instruments on AOCI (Details) - Pay fixed/receive floating swaps on borrowings cash flow hedges - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Derivative [Line Items]
Pay fixed/receive floating swaps on borrowings cash flow hedges	$ 31,225	$ (23,485)	$ 93,994	$ 67,198
Reclassification adjustment of net (gain)/loss included in net income	0	0	0	(14,110)
Total pre-tax gain/(loss) recognized in AOCI	$ 31,225	$ (23,485)	$ 93,994	$ 53,088