INVESTMENTS - Additional Information (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($) entity	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($) entity
Gain (Loss) on Securities [Line Items]
Proceeds from Sale of Debt Securities, Available-for-sale	$ 189,300	$ 135,400	$ 353,863	$ 347,403
Debt Securities, Available-for-sale, Realized Gain		700	3,500	1,100
Available-for-sale Securities, Gross Realized Losses		1,000	10,000	6,900
Debt Securities, Held-to-maturity, Allowance for Credit Loss	$ 0		$ 0		$ 0
NumberOfSecuritiesInSecurityPortfolio	740		740		743
NumberOfSecuritiesInUnrealizedLossPosition	534		534		644
Debt Securities, Held-to-maturity, Nonaccrual	$ 0		$ 0		$ 0
Net gain (loss) on investment securities	(42)	(17,468)	(9,748)	(22,719)
Debt Securities, Available-for-Sale, Unrealized Loss Position	1,923,991		1,923,991		2,531,876
Debt Securities, Unrealized Gain (Loss)			$ 9,100		$ 1,100
Net gain (loss) on equity securities				2,200
Debt Securities, Available-for-Sale, Realized Gain (Loss), Number \| entity			5		2
Debt Securities, Realized Gain (Loss)	3,400	$ 9,700	$ 3,400	$ 9,700
Financial Instrument, Other
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-Sale, Unrealized Loss Position	$ 21,000		$ 21,000		$ 11,100

Debt Securities, Available-for-Sale, Realized Gain (Loss), Number

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