SHORT-TERM BORROWINGS AND LONG-TERM DEBT (Narrative) (Details)		1 Months Ended		12 Months Ended
	Oct. 20, 2020 USD ($)	Dec. 31, 2004 USD ($)	Sep. 30, 2004 USD ($)	Dec. 31, 2025 USD ($) period	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
SHORT-TERM BORROWINGS
Maximum borrowing capacity				$ 1,800,000,000	$ 1,760,000,000
FHLB advances and other short-term borrowings				0	0	$ 0
Investments				1,381,925,000
Short-term borrowings				0	1,000	1,139,000
Long-term debt, net of unamortized debt issuance costs of $0 at December 31, 2025 and $202 at December 31, 2024				76,547,000	156,345,000
Long-term debt				7,143,000	9,079,000	8,633,000
Unamortized debt issuance costs				0	202,000
Maximum
SHORT-TERM BORROWINGS
Short-term borrowings				1,000	1,000
Central Bank | Federal Reserve Bank Advances
SHORT-TERM BORROWINGS
Additional unused borrowings available				206,400,000	232,100,000
Federal Home Loan Bank Borrowings
SHORT-TERM BORROWINGS
Standby letters of credit issued				95,600,000	83,600,000
Federal Home Loan Bank Borrowings | Asset Pledged as Collateral
SHORT-TERM BORROWINGS
Loans				2,760,000,000	3,140,000,000
Federal Reserve Bank Advances | Asset Pledged as Collateral
SHORT-TERM BORROWINGS
Loans				98,900,000	128,300,000
Investments				172,000,000.0	184,300,000
Pacific Coast Bankers' Bank ("PCBB")
SHORT-TERM BORROWINGS
Additional unused borrowings available				75,000,000.0	75,000,000.0
FHLB advances
SHORT-TERM BORROWINGS
Additional unused borrowings available				1,680,000,000	1,630,000,000
Long-term debt, net of unamortized debt issuance costs of $0 at December 31, 2025 and $202 at December 31, 2024				25,000,000	50,000,000
Long-term debt				1,300,000	2,200,000	$ 1,900,000
Junior Subordinated Debt | Trust IV
SHORT-TERM BORROWINGS
Long-term debt, net of unamortized debt issuance costs of $0 at December 31, 2025 and $202 at December 31, 2024				30,900,000
Trust preferred securities issued			$ 30,000,000.0
Variable rate basis			three-month LIBOR
Basis spread on variable rate			2.45%
Common securities issued to the Company			$ 900,000
Junior Subordinated Debt | Trust V
SHORT-TERM BORROWINGS
Long-term debt, net of unamortized debt issuance costs of $0 at December 31, 2025 and $202 at December 31, 2024				20,600,000
Trust preferred securities issued		$ 20,000,000.0
Variable rate basis		three-month LIBOR
Basis spread on variable rate		1.87%
Common securities issued to the Company		$ 600,000
Subordinated debentures
SHORT-TERM BORROWINGS
Long-term debt, net of unamortized debt issuance costs of $0 at December 31, 2025 and $202 at December 31, 2024				$ 51,547,000	51,547,000
Number of consecutive quarterly periods for which payments of interest can be deferred without default or penalty (up to) | period				20
Subordinated debentures | Maximum
SHORT-TERM BORROWINGS
Redemption period of trust preferred securities, the subordinated debentures and the common securities, following the occurrence of certain events				90 days
Senior Subordinated Notes
SHORT-TERM BORROWINGS
Long-term debt, net of unamortized debt issuance costs of $0 at December 31, 2025 and $202 at December 31, 2024				$ 0	54,798,000
Senior Subordinated Notes | Subordinated Notes
SHORT-TERM BORROWINGS
Long-term debt, net of unamortized debt issuance costs of $0 at December 31, 2025 and $202 at December 31, 2024					54,800,000
Basis spread on variable rate	4.56%
Debt face amount	$ 55,000,000.0
Debt instrument, term	10 years
Stated interest rate, first five years	4.75%
Unamortized debt issuance costs				$ 0	$ 202,000