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Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Other comprehensive (loss) income, net of tax: |  |  |
Unrealized net holding (losses) arising during the period , pre-tax amounts | $ (6,915) | $ (8,618) | $ (3,159)
Reclassification adjustment for net (gains) losses related to securities available for sale included in net income, pre-tax amounts | (1,869) | 644 | (3,087)
Reclassification adjustment for an impairment write-down of equity security, pre-tax amounts | 1,312 | 0 | 0
Unrealized gain on derivatives (cash flow hedges), pre-tax amounts | 609 | 2,901 | 0
Amortization of unrealized net gains and losses related to the reclassification of available for sale investment securities to held to maturity, pre-tax amounts | 875 | 1,094 | 1,311
Amortization of prior service cost and actuarial gains, pre-tax amounts | 1,852 | 2,370 | 2,239
Decrease (increase) in unrecognized actuarial loss, pre-tax amounts | $ 2,401 | $ 3,154 | $ (6,144)

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- Definition Amount before tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e689-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580 + Details
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