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MARKETABLE SECURITIES - Sale of Securities (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Sale of Marketable Securities [Abstract] |  |  |
Proceeds | $ 217,111 | $ 105,808 | $ 140,668
Gross gains | 180 | 243 | 222
Gross losses | (13) | (161) | (145)
Held-to-maturity Securities, Sales, Excluding Other than Temporary Impairments [Abstract] |  |  |
Proceeds from sales | 3,298 | 1,866 | 0
Amortized cost | 3,140 | 1,842 | 0
Gross realized gains | 158 | 24 | 0
Gross realized losses | 0 | 0 | 0
Tax expense related to securities gains/losses | $ (44) | $ (7) | $ 0

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- Definition Held-to-maturity Securities, Sold Security, Amortized Cost + References No definition available. + Details
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- Definition The cash inflow associated with the sale of securities that had been designated as held-to-maturity. Excludes proceeds from maturities, prepayments and calls by the issuer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26853-111562 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3179-108585 + Details
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