Securities - Schedule of Amortized Cost and Fair Value of Investment Securities Portfolio by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Available for sale
Three months or less	$ 0
Over three months through one year	0
Over one year through five years	1,609
Over five years through ten years	37,406
Over ten years	216,434
Amortized Cost	648,230	$ 1,051,436
Fair Value
Three months or less	0
Over three months through one year	0
Over one year through five years	1,641
Over five years through ten years	37,918
Over ten years	218,850
Total	652,132	1,030,668
Asset-backed securities
Available for sale
Amortized Cost		25,744
Fair Value
Total		24,844
Mortgage-backed securities: residential
Available for sale
Amortized Cost, Mortgage-backed securities not due at a single maturity date	374,923
Amortized Cost	374,923	596,766
Fair Value
Mortgage-backed securities not due at a single maturity date	375,943
Total	375,943	$ 580,699
Mortgage-backed securities: commercial
Available for sale
Amortized Cost, Mortgage-backed securities not due at a single maturity date	17,858
Amortized Cost	17,858
Fair Value
Mortgage-backed securities not due at a single maturity date	17,780
Total	$ 17,780

Available for sale securities debt maturities within three months amortized cost.

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Available for sale securities debt maturities within three months fair value.

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Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Over Three Months To One Year, Amortized Cost

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Amortized cost of 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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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth fiscal year through tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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