Borrowed Funds (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Sep. 30, 2021
Debt Disclosure [Abstract]
Interest rate swaps, remaining term to maturity			3 years 3 months 18 days		4 years 1 month 6 days
Interest rate swaps, fair value	$ 1,300		$ 1,300		$ (27,700)
Derivative Asset, balance sheet location	Other assets		Other assets
Derivative Liability, balance sheet location					Other Liabilities
Interest rate swaps, amount reclassified from AOCI	$ 1,301	$ 2,124	$ 4,797	$ 11,515
Interest rate swaps, amount reclassified from AOCI as an increase to interest expense				7,900
Loss on interest rate swap termination, net of tax				3,600
Interest rate swaps, future amount to be reclassified from AOCI			(1,400)
Interest rate swaps, collateral held	(2,600)		(2,600)
Interest rate swaps, collateral posted					$ 28,000
Loss on interest rate swap termination	0	0	0	4,752
Debt Instrument [Line Items]
Interest rate swaps, notional amount	365,000		365,000
Interest rate swaps, notional amount					365,000
FHLB advances, variable rate	365,000		365,000		$ 365,000
Leverage Strategy [Member]
Debt Instrument [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available	$ 2,100,000		$ 2,100,000
Terminated Interest Rate Swaps [Member]
Debt Instrument [Line Items]
Interest rate swaps, notional amount		200,000		200,000
FHLB advances, variable rate		$ 200,000		$ 200,000