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GOODWILL AND OTHER INTANGIBLES - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Feb. 01, 2026	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Goodwill [Line Items]
Goodwill		$ 788,186	$ 712,002	$ 788,186	$ 712,002	$ 712,002	$ 712,002
Intangible asset amortization		$ 2,706	$ 1,505	$ 5,008	$ 3,031
Minimum
Goodwill [Line Items]
Useful life of core deposit intangibles and other intangibles		1 year		1 year
Maximum
Goodwill [Line Items]
Useful life of core deposit intangibles and other intangibles		10 years		10 years
First Savings
Goodwill [Line Items]
Goodwill	$ 76,184
Other intangibles acquired	30,200
First Savings \| Core Deposits
Goodwill [Line Items]
Other intangibles acquired	$ 29,400
Useful life of core deposit intangibles and other intangibles	10 years
First Savings \| Other Intangible Assets
Goodwill [Line Items]
Other intangibles acquired	$ 800
Useful life of core deposit intangibles and other intangibles	1 year