GOODWILL, CORE DEPOSIT PREMIUM AND OTHER INTANGIBLE ASSETS (Carrying amount of intangible assets (including accumulated amortization) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 122,643	$ 122,206
Accumulated Amortization	83,607	82,328
Net Carrying Amount	39,036	39,878
Core deposit intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	101,185	101,185
Accumulated Amortization	70,375	68,330
Net Carrying Amount	30,810	32,855
Customer relationship intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,177	1,177
Accumulated Amortization	1,053	1,044
Net Carrying Amount	124	133
Mortgage servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	13,227	12,790
Accumulated Amortization	5,125	6,378
Net Carrying Amount	8,102	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