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Commitments and Contingencies (Narrative) (Details) $ in Thousands	6 Months Ended		9 Months Ended
	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($) entity	Sep. 30, 2024	Apr. 23, 2025 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Financial guarantees in connection with standby letters of credit	$ 0	$ 0
Standby letters of credit expiring within one year	295,200
Standby letters of credit expiring thereafter	26,000
Loss Contingency Accrual	1,200
Concentration Risk [Line Items]
Loss Contingency Accrual	1,200
Columbia Banking Systems and Pacific Premier Bancorp Merger
Concentration Risk [Line Items]
Termination Fee				$ 75,000
iCap Entities [Member]
Concentration Risk [Line Items]
Number of Defendant Entities | entity		34
Loss Contingency, Damages Sought, Value	290,000
Professional Financial Investors, Inc. and Professional Investors Security Fund, Inc. [Member]
Commitments and Contingencies Disclosure [Abstract]
Loss Contingency Accrual	55,000
Concentration Risk [Line Items]
Loss Contingency Accrual	55,000
Minimum | Professional Financial Investors, Inc. and Professional Investors Security Fund, Inc. [Member]
Concentration Risk [Line Items]
Loss Contingency, Damages Sought, Value	297,400
Maximum | Professional Financial Investors, Inc. and Professional Investors Security Fund, Inc. [Member]
Concentration Risk [Line Items]
Loss Contingency, Damages Sought, Value	$ 368,100
Product Concentration Risk | Revenue Benchmark | Real Estate Loans As Part Of Loan Portfolio
Concentration Risk [Line Items]
Concentration risk (as a percent)	75.00%		75.00%
Product Concentration Risk | Revenue Benchmark | Multifamily Loans as Part of Loan portfolio [Member]
Concentration Risk [Line Items]
Concentration risk (as a percent)	19.00%		19.00%
Product Concentration Risk | Revenue Benchmark | Commercial Office Loans as Part of Loan portfolio [Member]
Concentration Risk [Line Items]
Concentration risk (as a percent)	8.00%		8.00%

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