GOODWILL, OTHER INTANGIBLE ASSETS AND MORTGAGE SERVICING RIGHTS (Finite-Lived Intangible Assets) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Goodwill, beginning of period	$ 373,121	$ 373,121
Goodwill, end of period	373,121	373,121
Finite-lived Intangible Assets [Roll Forward]
Goodwill and other intangibles, net, beginning of period	394,547	402,279
Amortization	(3,422)	(7,732)
Goodwill and other intangibles, net, end of period	391,125	394,547
Core Deposit Intangibles [Member]
Finite-lived Intangible Assets [Roll Forward]
Finite lived assets Balance, beginning of period	21,426	29,158
Amortization	(3,422)	(7,732)
Finite lived assets Balance, end of period	$ 18,004	$ 21,426

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Carrying amount of finite-lived intangible assets, indefinite-lived intangible assets and goodwill. Goodwill is an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. Intangible assets are assets, not including financial assets, lacking physical substance.

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