GOODWILL, CORE DEPOSIT PREMIUM AND OTHER INTANGIBLE ASSETS (Estimated future amortization expense for amortizable intangible assets) (Details) $ in Thousands	Mar. 31, 2021 USD ($)
Future amortization expense for amortizable intangible assets [Line Items]
Nine months ending December 31, 2021	$ 8,257
Year ending December 31,
2022	9,197
2023	7,996
2024	6,618
2025	5,553
2026	4,071
Thereafter	5,128
Total	46,820
Core Deposit Intangibles
Future amortization expense for amortizable intangible assets [Line Items]
Nine months ending December 31, 2021	6,852
Year ending December 31,
2022	7,702
2023	6,739
2024	5,591
2025	4,700
2026	3,533
Thereafter	4,591
Total	39,708
Customer Relationship Intangibles
Future amortization expense for amortizable intangible assets [Line Items]
Nine months ending December 31, 2021	27
Year ending December 31,
2022	34
2023	33
2024	33
2025	32
2026	0
Thereafter	0
Total	159
Mortgage Servicing Rights
Future amortization expense for amortizable intangible assets [Line Items]
Nine months ending December 31, 2021	1,201
Year ending December 31,
2022	1,254
2023	1,075
2024	896
2025	717
2026	538
Thereafter	537
Total	6,218
Commercial Servicing Rights
Future amortization expense for amortizable intangible assets [Line Items]
Nine months ending December 31, 2021	177
Year ending December 31,
2022	207
2023	149
2024	98
2025	104
2026	0
Thereafter	0
Total	$ 735

Future amortization expense for amortizable intangible assetse [Line Items]

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Amount of amortization for asset, excluding financial asset and goodwill, lacking physical substance with finite life expected to be recognized after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in remainder of current fiscal year.

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 926
-SubTopic 20
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=120154696&loc=d3e54445-107959

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