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 ($)		12 Months Ended
	Aug. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill impairment	$ 0
Amortization of other intangible assets		$ 16,911,000	$ 14,442,000	$ 11,841,000
Impairment charges		$ 0	$ 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