FAIR VALUE MEASUREMENTS - Unobservable Inputs Non-recurring (Details) $ in Thousands	Sep. 30, 2020 USD ($) security	Dec. 31, 2019 USD ($) security
Quantitative information about the significant unobservable inputs within Level 3
Other Real Estate Owned (2)	$ 40	$ 0
Non-recurring | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Individually evaluated loans	41,312	8,831
Capitalized servicing rights	13,694	14,152
Other Real Estate Owned (2)	401	0
Total	55,407	22,983
Non-recurring | Fair Value of Collateral | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Individually evaluated loans	$ 41,312	$ 8,831
Non-recurring | Minimum | Loss severity | Fair Value of Collateral | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans, significant unobservable input value	0.0004	0.1572
Non-recurring | Minimum | Appraised value | Fair Value of Collateral | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans, significant unobservable input value	0	8
Non-recurring | Maximum | Loss severity | Fair Value of Collateral | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans, significant unobservable input value	1.0000	0.0012
Non-recurring | Maximum | Appraised value | Fair Value of Collateral | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans, significant unobservable input value	10,972	1,548
Non-recurring | Weighted Average | Loss severity | Fair Value of Collateral | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans, significant unobservable input value	0.4831	0.0450
Non-recurring | Weighted Average | Appraised value | Fair Value of Collateral | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans, significant unobservable input value	8,258	736
Non-recurring | Capitalized servicing rights | Discounted Cash Flow | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Capitalized servicing rights	$ 13,694	$ 14,152
Non-recurring | Capitalized servicing rights | Minimum | Constant prepayment rate (CPR) | Discounted Cash Flow | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Servicing asset, significant unobservable input value	0.1498	0.0944
Non-recurring | Capitalized servicing rights | Minimum | Discount rate | Discounted Cash Flow | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Servicing asset, significant unobservable input value	0.0825	0.1000
Non-recurring | Capitalized servicing rights | Maximum | Constant prepayment rate (CPR) | Discounted Cash Flow | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Servicing asset, significant unobservable input value	0.2205	0.1412
Non-recurring | Capitalized servicing rights | Maximum | Discount rate | Discounted Cash Flow | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Servicing asset, significant unobservable input value	0.1100	0.1350
Non-recurring | Capitalized servicing rights | Weighted Average | Constant prepayment rate (CPR) | Discounted Cash Flow | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Servicing asset, significant unobservable input value	0.1708	0.1225
Non-recurring | Capitalized servicing rights | Weighted Average | Discount rate | Discounted Cash Flow | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Servicing asset, significant unobservable input value	0.0917	0.1178
Other Real Estate Owned | Non-recurring | Fair Value of Collateral | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Other Real Estate Owned (2)	$ 401	$ 0
Other Real Estate Owned | Non-recurring | Appraised value | Fair Value of Collateral | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Other real estate owned, significant unobservable input value | security		0
Other Real Estate Owned | Non-recurring | Minimum | Appraised value | Fair Value of Collateral | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Other real estate owned, significant unobservable input value | security	94
Other Real Estate Owned | Non-recurring | Maximum | Appraised value | Fair Value of Collateral | Level 3
Quantitative information about the significant unobservable inputs within Level 3
Other real estate owned, significant unobservable input value | security	361