LOANS & ALLOWANCE FOR CREDIT LOSSES - NARRATIVE (Details)		12 Months Ended
Dec. 07, 2023 loanPortfolio	Jun. 30, 2025 USD ($) segment	Jun. 30, 2024 USD ($)
Financing Receivable, Impaired [Line Items]
Number of loan portfolio segments	2	5
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]		Other assets	Other assets
Accrued interest receivable		$ 109,600,000	$ 119,800,000
Advances, collateral pledged		4,284,700,000	4,942,800,000
FRBSF and FRB, loans pledged		8,227,700,000	8,197,200,000
Nonaccrual loans, without an allowance		0	0
Interest recognized on performing loans temporarily modified as TDRs		0	0
Loans past due ninety days or more and still accruing		0	20,200,000
Mortgage loans in process of foreclosure, amount		$ 30,400,000	$ 20,100,000
California \| Financing Receivable \| Geographic Concentration Risk \| Single Family - Mortgage & Warehouse
Financing Receivable, Impaired [Line Items]
Concentration risk percentage		70.50%	69.30%
California \| Financing Receivable \| Geographic Concentration Risk \| Multifamily Loan Category
Financing Receivable, Impaired [Line Items]
Concentration risk percentage		48.50%	49.60%
New York \| Financing Receivable \| Geographic Concentration Risk \| Single Family - Mortgage & Warehouse
Financing Receivable, Impaired [Line Items]
Concentration risk percentage		8.60%	11.70%
New York \| Financing Receivable \| Geographic Concentration Risk \| Multifamily Loan Category
Financing Receivable, Impaired [Line Items]
Concentration risk percentage		37.10%	38.90%
New York \| Financing Receivable \| Geographic Concentration Risk \| Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Concentration risk percentage		36.80%	34.20%
FLORIDA \| Financing Receivable \| Geographic Concentration Risk \| Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Concentration risk percentage		19.50%	10.40%
TEXAS \| Financing Receivable \| Geographic Concentration Risk \| Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Concentration risk percentage		10.20%

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Financing Receivable, Interest Income, Performing Loans Temporarily Modified As TDRs

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Amount of the collateral pledged in support of federal home loan bank advances outstanding.

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Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

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