LOANS AND ALLOWANCE FOR CREDIT LOSSES - Amortized Cost Basis of Collateral Dependent Loans Individually Evaluated to Determine Expected Credit Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	$ 40,068	$ 31,251
Real Estate
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	37,024	17,541
Business Assets
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	3,044	13,654
Other
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	56
Commercial and industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	3,044	13,654
Commercial and industrial \| Real Estate
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Commercial and industrial \| Business Assets
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	3,044	13,654
Commercial and industrial \| Other
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Real estate: \| Commercial real estate (including multi-family residential)
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	24,029	3,552
Real estate: \| Commercial real estate (including multi-family residential) \| Real Estate
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	24,029	3,552
Real estate: \| Commercial real estate (including multi-family residential) \| Business Assets
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Real estate: \| Commercial real estate (including multi-family residential) \| Other
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Real estate: \| Commercial real estate construction and land development
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	2,899	577
Real estate: \| Commercial real estate construction and land development \| Real Estate
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	2,899	577
Real estate: \| Commercial real estate construction and land development \| Business Assets
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Real estate: \| Commercial real estate construction and land development \| Other
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Real estate: \| 1-4 family residential (including home equity)
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	9,639	13,412
Real estate: \| 1-4 family residential (including home equity) \| Real Estate
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	9,639	13,412
Real estate: \| 1-4 family residential (including home equity) \| Business Assets
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Real estate: \| 1-4 family residential (including home equity) \| Other
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Real estate: \| Residential construction
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	457	0
Real estate: \| Residential construction \| Real Estate
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	457	0
Real estate: \| Residential construction \| Business Assets
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Real estate: \| Residential construction \| Other
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Consumer and other
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	56
Consumer and other \| Real Estate
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Consumer and other \| Business Assets
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	0	0
Consumer and other \| Other
Financing Receivable Allowance For Credit Losses [Line Items]
Finance receivables allowance of credit losses	$ 0	$ 56

Stellar Bancorp, Inc. 10-Q