Summary of Significant Accounting Policies (Cumulative Effect Adjustment) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Summary Of Significant Accounting Policies [Line Items]
ACL	$ 24,178	$ 23,759	$ 19,189	$ 16,371
Reserve for off-balance sheet credit exposures	3,834	4,095	5,591	4,751
Cumulative effect adjustment	$ (1,034,121)	(1,044,054)	$ (1,054,795)	$ (1,096,499)
Accounting Standards Update 2022-02 Cumulative Effect, Period of Adoption [Member] | Accounting Standards Update 2022-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL		20
Reserve for off-balance sheet credit exposures		$ 16