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Securities - Additional Information (Detail) $ in Thousands	Mar. 31, 2019 USD ($) Investment	Dec. 31, 2018 USD ($) Investment
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

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

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