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LOANS - Narrative (Details) $ in Thousands | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2018 USD ($) contract | Mar. 31, 2017 contract | Dec. 31, 2016 USD ($) | Dec. 31, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Total loans | $ 8,376,417 |  |  | $ 8,299,338
Borrower's sustained repayment performance period | 6 months |  |  |
Modifications that subsequently defaulted, number of contracts | contract | 0 | 2 |  |
Residential Mortgages |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Total loans | $ 2,181,807 |  |  | 2,102,807
Residential Mortgages | Mortgages |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Process of foreclosure | 7,200 |  | $ 4,900 |
Acquired Loans |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Total loans | 2,093,739 |  |  | 2,187,140
Acquired Credit Impaired | 93,645 |  |  | 97,344
Certain loans acquired in transfer not accounted for as debt securities, note balance, net | 202,800 |  |  | 208,700
Financing receivable not considered impaired at time of acquisition | 2,000,000 |  |  | 2,100,000
Acquired Loans | Residential Mortgages |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Total loans | 275,094 |  |  | 289,606
Acquired Credit Impaired | 6,903 |  |  | 6,974
Acquired Loans | Residential Mortgages | Mortgages |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Total loans | $ 275,094 |  |  | $ 289,606

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- Definition Represents the reasonable period of a borrower's sustained repayment performance for consideration of returning the loan to performing status. + References No definition available. + Details
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- Definition The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538 + Details
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- Definition Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524 + Details
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