The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

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Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Goodwill [Line Items]
Amortization of other intangible assets	$ 4,325,000	$ 3,416,000	$ 8,797,000	$ 7,025,000
Impairment charges			$ 0	$ 0
Core Deposits and Other Intangible Assets [Member] \| Minimum [Member]
Goodwill [Line Items]
Estimated useful lives of core deposits and customer relationships			5 years
Core Deposits and Other Intangible Assets [Member] \| Maximum [Member]
Goodwill [Line Items]
Estimated useful lives of core deposits and customer relationships			15 years