FAIR VALUE MEASUREMENTS - Unobservable Inputs Non-recurring (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Quantitative information about the significant unobservable inputs within Level 3
Other real estate owned	$ 216	$ 122
Non-recurring \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Total	20,038	15,073
Non-recurring \| Fair value of collateral -appraised value \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans	13,364	8,586
Other real estate owned	216	122
Non-recurring \| Discount cash flow \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans	1,763	2,207
Capitalized servicing rights	4,695	4,158
Non-recurring \| Impaired loans \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Impaired loans	$ 15,127	$ 10,793
Non-recurring \| Impaired loans \| Minimum \| Fair value of collateral -appraised value \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Loss severity	0.00%	15.70%
Appraised value	$ 100	$ 100
Non-recurring \| Impaired loans \| Minimum \| Discount cash flow \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Discount rate	2.88%	2.63%
Cash flows	$ 26	$ 6
Non-recurring \| Impaired loans \| Maximum \| Fair value of collateral -appraised value \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Loss severity	54.00%	45.28%
Appraised value	$ 6,915	$ 7,545
Non-recurring \| Impaired loans \| Maximum \| Discount cash flow \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Discount rate	9.50%	9.50%
Cash flows	$ 570	$ 320
Non-recurring \| Capitalized servicing rights \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Capitalized servicing rights	$ 4,695	$ 4,158
Non-recurring \| Capitalized servicing rights \| Discount cash flow \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Discount rate	10.10%	10.10%
Constant prepayment rate (CPR)	9.22%	10.97%
Non-recurring \| Other real estate owned \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Other real estate owned	$ 216	$ 122
Non-recurring \| Other real estate owned \| Fair value of collateral -appraised value \| Level 3
Quantitative information about the significant unobservable inputs within Level 3
Appraised value	$ 216	$ 122

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- Definition

Fair Value Inputs, Cash Flow

+ References

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- Definition

Represents the amount of impaired loans assets reported on the balance sheet at period end measured at fair value by the entity.

+ References

No definition available.

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

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- Definition

Loss, including interest and principal, incurred on a defaulted security, expressed as a percentage of the original principal balance, used as an input to measure fair value.

+ References

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-Publisher FASB
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-Section 50
-Paragraph 2
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- Definition

Rate at which loans or a loan portfolio are expected to prepay principal balances, used as an input to measure fair value.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 2
-Subparagraph (bbb)
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- Definition

Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
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- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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