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Investment Securities - Proceeds from Sale, Gross Gains (Losses) Realized on Sales, Maturities and Other-Than-Temporary Impairment Charges Related to Securities Available for Sale (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract] |  |  |
Proceeds from sale | $ 55,744 | $ 88,054 | $ 132,868
Sales Transactions: |  |  |
Gross gains | 305 | 0 | 291
Gross losses | (277) | (284) | (243)
Total gain (losses) from sales transactions | 28 | (284) | 48
Maturities, calls and impairment: |  |  |
Gross gains | 589 | 131 | 502
Gross losses | 0 | 0 | 0
Other-than-temporary impairment | 0 | 0 | 0
Total gain (losses) maturities and impairment | 589 | 131 | 502
Net gains (losses) and impairment | $ 617 | $ (153) | $ 550

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- Definition This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27357-111563 + Details
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- Definition The total amount of proceeds received for the sale of securities, categorized neither as held-to-maturity nor trading securities, during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27357-111563 + Details
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