OTHER BORROWINGS - Narrative (Details)	3 Months Ended
Mar. 31, 2019 USD ($)
Debt Instrument [Line Items]
Federal home loan bank, advances, general debt obligations, amount of available, unused funds	$ 2,040,000,000
Credit arrangements for federal funds purchase	117,000,000
Pledged assets separately reported, loans pledged for federal reserve bank, at fair value	1,600,000,000
Loans pledged at federal reserve discount window available for borrowing	1,110,000,000
Advances under revolving credit agreement with a regional bank due September 26, 2020; secured by subsidiary bank stock; variable interest rate at 90-day LIBOR plus 3.50% (6.13% at March 31, 2019)
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 100,000,000.0
Basis spread on variable rate	3.50%
Line of credit facility, remaining borrowing capacity	$ 30,000,000

Borrowing capacity available based on pledged collateral.

No definition available.

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- Definition

Federal funds purchased maximum capacity.

+ References

No definition available.

+ Details

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

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

Amount of advances or credit lines available from the Federal Home Loan Bank (FHLB).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22 (b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(3)(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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- Definition

The fair value, as of the date of each statement of financial position presented, of loans which are owned but transferred to serve as collateral for the payment of other debt obligations, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

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