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	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Debt Securities, Available-for-sale [Line Items]
Proceeds from sales of available-for-sale debt securities	$ 258,951	$ 47,064	$ 267,632	$ 131,321
Proceeds from calls of available-for-sale debt securities			335,035	220,753
Total	297,381	58,275	329,747	159,968
Realized gains on sales of available-for-sale debt securities	3,032	1,251	3,103	3,259
Realized losses on sales of available-for-sale debt securities	(1,867)	(48)	(2,015)	(1,305)
Other securities gains (losses)		12		97
Net debt securities gains (losses)	1,165	1,494	1,062	2,282
Calls [Member]
Debt Securities, Available-for-sale [Line Items]
Proceeds from calls of available-for-sale debt securities	$ 38,430	11,211	62,115	28,647
Realized gains on calls of available-for-sale debt securities		283	3	284
Realized losses on calls of available-for-sale debt securities		$ (4)	$ (29)	$ (53)

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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