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Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Financial guarantees in connection with standby letters of credit	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Standby letters of credit expiring within one year	203.3		203.3
Standby letters of credit expiring thereafter	35.4		35.4
Loss Contingency Accrual	2.4		2.4
Concentration Risk [Line Items]
Prior Bankruptcy Recoveries by Plaintiffs	$ 110.0		110.0
iCap Entities [Member]
Concentration Risk [Line Items]
Number of Defendant Entities				34
Loss Contingency, Damages Sought, Value			290.0
Minimum | Professional Financial Investors, Inc. and Professional Investors Security Fund, Inc. [Member]
Concentration Risk [Line Items]
Loss Contingency, Damages Sought, Value			386.2
Maximum | Professional Financial Investors, Inc. and Professional Investors Security Fund, Inc. [Member]
Concentration Risk [Line Items]
Loss Contingency, Damages Sought, Value			$ 429.8
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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