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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Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
	Aug. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Goodwill [Line Items]
Goodwill impairment	$ 0
Impairment charges				$ 0	$ 0
Amortization of other intangible assets		$ 3,459,000	$ 4,168,000	$ 10,847,000	$ 12,965,000
Core Deposits and Other Intangible Assets \| Minimum
Goodwill [Line Items]
Estimated useful lives of core deposits and customer relationships				5 years
Core Deposits and Other Intangible Assets \| Maximum
Goodwill [Line Items]
Estimated useful lives of core deposits and customer relationships				15 years