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Securities - Additional Information (Detail) $ in Thousands | Mar. 31, 2017 USD ($) Investment | Dec. 31, 2016 USD ($) Investment
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Schedule of Investments [Line Items] |  |  |
Federal Home Loan Bank stock, at cost | [1] | $ 577,943 | $ 590,934
Investment securities designated as having a continuous loss position for twelve months or more, unrealized losses |  | $ 11,900 | $ 14,100
Investment securities designated as having a continuous loss position for twelve months or more, percentage below collective amortized cost |  | 27.30% | 32.20%
Investment securities designated as having a continuous loss position for twelve months or more, amortized cost |  | $ 43,700 | $ 43,700
Capital trust notes |  |  |
Schedule of Investments [Line Items] |  |  |
Number of investment securities designated as having a continuous loss position for twelve months or more | Investment |  | 5 | 5
[1] | Carrying value and estimated fair value are at cost.

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- Definition Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses. + References No definition available. + Details
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- Definition Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 325 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6478792&loc=d3e63345-112809 + Details
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