Amount, after tax, of accumulated unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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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).

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The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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The maximum percentage of shareholders' equity of any one issuer other than the U.S. government and its agencies.

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Reclassification of callable held -to- maturity securities.

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Schedule of available for sale securities and held to maturity.

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Securities - Additional Information (Detail) $ in Thousands	12 Months Ended
Securities - Additional Information (Detail) $ in Thousands	Dec. 31, 2019 USD ($) Holding	Dec. 31, 2018 USD ($) Holding	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Maximum percentage of equity of one issuer	10.00%
Number of holdings greater than specified percentage of equity \| Holding	0	0
Equities securities	$ 12,343	$ 11,737
Securities with aggregate fair values	2,000,000	2,000,000
Proceeds from sale of available-for-sale securities	125,839	82,134	$ 7,760
Net unrealized gains (losses) on available-for-sale securities included in AOCI	20,700	(21,500)	$ (13,300)
Federal home loan bank stock, Total	66,800	$ 50,800
Accounting Standards Update 2017-12 [Member] \| Municipal Debt Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Reclassification of callable held-to-maturity securities				$ 67,300
Grantor Trusts [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Equities securities	$ 8,900