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Securities - Additional Information (Detail) $ in Thousands | Mar. 31, 2019 USD ($) Investment | Dec. 31, 2018 USD ($) Investment
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Schedule of Investments [Line Items] |  |
Federal Home Loan Bank stock, at cost | $ | $ 588,197 | $ 644,590
Investment securities designated as having a continuous loss position for twelve months or more, unrealized losses | $ | $ 16,100 | $ 22,500
Investment securities designated as having a continuous loss position for twelve months or more, percentage below collective amortized cost | 1.90% | 2.90%
Investment securities designated as having a continuous loss position for twelve months or more, amortized cost | $ | $ 829,800 | $ 782,400
Mortgage-Related Securities |  |
Schedule of Investments [Line Items] |  |
Number of investment securities designated as having a continuous loss position for twelve months or more | 12 | 9
Capital trust notes |  |
Schedule of Investments [Line Items] |  |
Number of investment securities designated as having a continuous loss position for twelve months or more | 5 | 5
Municipal bonds |  |
Schedule of Investments [Line Items] |  |
Number of investment securities designated as having a continuous loss position for twelve months or more | 3 | 3
Mutual Fund |  |
Schedule of Investments [Line Items] |  |
Number of investment securities designated as having a continuous loss position for twelve months or more | 1 | 1
US Government agencies securities |  |
Schedule of Investments [Line Items] |  |
Number of investment securities designated as having a continuous loss position for twelve months or more | 4 | 9
Collateralized mortgage obligations |  |
Schedule of Investments [Line Items] |  |
Number of investment securities designated as having a continuous loss position for twelve months or more | 9 | 7

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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 Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Amortized Cost. + 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 325 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=75031641&loc=d3e63345-112809 + Details
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