GOODWILL AND OTHER INTANGIBLE ASSETS - Gross Carrying Amounts and Accumulated Amortization (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 42,944	$ 42,944
Accumulated Amortization	(18,532)	(17,024)
Net Carrying Amount	24,412	25,920
Goodwill	370,223	370,223
Goodwill	370,223	370,223
Core deposit intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	29,038	29,038
Accumulated Amortization	(13,678)	(12,624)
Net Carrying Amount	$ 15,360	$ 16,414
Core deposit intangibles | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Life	7 years 2 months 12 days	7 years 4 months 24 days
Other identifiable intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 13,906	$ 13,906
Accumulated Amortization	(4,854)	(4,400)
Net Carrying Amount	$ 9,052	$ 9,506
Other identifiable intangibles | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Life	9 years 6 months	9 years 8 months 12 days