GOODWILL, CORE DEPOSIT PREMIUM AND OTHER INTANGIBLE ASSETS (Carrying amount of intangible assets (including accumulated amortization) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 123,424	$ 122,206
Accumulated Amortization	88,050	82,328
Net Carrying Amount	35,374	39,878
Core deposit intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	101,185	101,185
Accumulated Amortization	74,190	68,330
Net Carrying Amount	26,995	32,855
Customer relationship intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,177	1,177
Accumulated Amortization	1,177	1,044
Net Carrying Amount	0	133
Mortgage servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	14,008	12,790
Accumulated Amortization	5,629	6,378
Net Carrying Amount	8,379	6,412
Commercial servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,054	7,054
Accumulated Amortization	7,054	6,576
Net Carrying Amount	$ 0	$ 478