FAIR VALUE MEASURES - Summary of Significant Unobservable Inputs Used in Fair Value Measurement of Level 3 Assets and Liabilities (Details) $ in Thousands	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, at fair value	$ 1,403,403	$ 1,192,423
Purchased other real estate owned	4,500	7,218
Fair Value, Measurements, Recurring | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, at fair value	1,500	1,500
Fair Value, Measurements, Nonrecurring | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total impaired loans	43,788	28,653
Other real estate owned	2,289	408
Purchased other real estate owned	$ 15,000	$ 9,535
Discounted par values | Credit quality of underlying issuer | Fair Value, Measurements, Recurring | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, measurement input	0	0
Discounted par values | Credit quality of underlying issuer | Fair Value, Measurements, Recurring | Weighted Average | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, measurement input	0	0
Third party appraisals and discounted cash flows | Collateral discounts and discount rates | Fair Value, Measurements, Nonrecurring | Minimum | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired loans, measurement input	0.01	0.03
Third party appraisals and discounted cash flows | Collateral discounts and discount rates | Fair Value, Measurements, Nonrecurring | Maximum | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired loans, measurement input	0.95	0.53
Third party appraisals and discounted cash flows | Collateral discounts and discount rates | Fair Value, Measurements, Nonrecurring | Weighted Average | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired loans, measurement input	0.27	0.30
Third party appraisals and sales contracts | Collateral discounts and estimated costs to sell | Fair Value, Measurements, Nonrecurring | Minimum | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned, measurement input	0.15	0.15
Third party appraisals and sales contracts | Collateral discounts and estimated costs to sell | Fair Value, Measurements, Nonrecurring | Maximum | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned, measurement input	0.31	0.69
Third party appraisals and sales contracts | Collateral discounts and estimated costs to sell | Fair Value, Measurements, Nonrecurring | Weighted Average | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned, measurement input	0.25	0.31
Third party appraisals | Collateral discounts and estimated costs to sell | Fair Value, Measurements, Nonrecurring | Minimum | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Purchased other real estate owned, measurement input	0.09	0.06
Third party appraisals | Collateral discounts and estimated costs to sell | Fair Value, Measurements, Nonrecurring | Maximum | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Purchased other real estate owned, measurement input	0.89	0.74
Third party appraisals | Collateral discounts and estimated costs to sell | Fair Value, Measurements, Nonrecurring | Weighted Average | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Purchased other real estate owned, measurement input	0.31	0.39