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		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Derivative [Line Items]
Pay fixed/receive floating swaps on borrowings cash flow hedges	$ (21,972)	$ 56,323	$ (28,778)	$ 62,769
Total pre-tax gain/(loss) recognized in AOCI	$ (21,972)	$ 56,323	$ (28,778)	$ 62,769