GOODWILL, OTHER INTANGIBLE ASSETS AND MORTGAGE SERVICING RIGHTS (Finite-Lived Intangible Assets) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Goodwill [Roll Forward]
Goodwill, beginning of period	$ 373,121	$ 373,121
Goodwill, end of period	373,121
Finite-lived Intangible Assets [Roll Forward]
Intangible Assets, Net (Including Goodwill)	379,663		$ 382,561	$ 387,976
Amortization	(2,898)	(5,279)
Core Deposit Intangibles [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite-Lived Intangible Assets, Net	6,542		$ 9,440	$ 14,855
finite-lived intangible assets, other changes		136
Amortization	$ (2,898)	$ (5,279)