Investment Securities - Schedule of Proceeds from Sales or Calls and Realized Gain and Losses of Available-for-sale Investment Securities and Other Securities (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Debt Securities, Available-for-sale [Line Items]
Proceeds from sales of available-for-sale debt securities	$ 27,983	$ 5,327	$ 295,615	$ 136,648
Proceeds from calls of available-for-sale debt securities			810,397	316,239
Total	344,344	8,265	674,091	168,233
Realized gains on sales of available-for-sale debt securities	340		3,443	3,259
Realized losses on sales of available-for-sale debt securities	(2)	(74)	(2,017)	(1,379)
Other securities gains (losses)		216		313
Net debt securities gains (losses)	424	135	1,486	2,417
Calls [Member]
Debt Securities, Available-for-sale [Line Items]
Proceeds from calls of available-for-sale debt securities	316,361	2,938	378,476	31,585
Realized gains on calls of available-for-sale debt securities	$ 86		89	284
Realized losses on calls of available-for-sale debt securities		$ (7)	$ (29)	$ (60)

The gross profit realized on the call of available-for-sale debt or equity securities.

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The gross loss realized on the call of available-for-sale debt or equity securities.

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Amount of unrealized and realized gain (loss) on investment in debt and equity securities.

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Amount of realized gain 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 realized 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 unrealized and realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

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Amount of cash inflow from maturity, prepayment and call 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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Amount of cash inflow from sale, maturity, prepayment and call 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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Amount of cash inflow from sale 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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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