Goodwill and Other Intangibles - Summary of Goodwill and Other Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Balances not subject to amortization
Goodwill	$ 369,477	$ 369,477
Balances subject to amortization
Total other intangible assets	6,525	7,057
Total goodwill and other intangible assets	376,002	376,534
Insurance agency
Balances subject to amortization
Balances subject to amortization	6,398	6,899
Core deposits
Balances subject to amortization
Balances subject to amortization	127	158
Banking Business
Balances not subject to amortization
Goodwill	298,611	298,611
Balances subject to amortization
Total other intangible assets	127	158
Total goodwill and other intangible assets	298,738	298,769
Banking Business \| Insurance agency
Balances subject to amortization
Balances subject to amortization	0	0
Banking Business \| Core deposits
Balances subject to amortization
Balances subject to amortization	127	158
Insurance Agency Business
Balances not subject to amortization
Goodwill	70,866	70,866
Balances subject to amortization
Total other intangible assets	6,398	6,899
Total goodwill and other intangible assets	77,264	77,765
Insurance Agency Business \| Insurance agency
Balances subject to amortization
Balances subject to amortization	6,398	6,899
Insurance Agency Business \| Core deposits
Balances subject to amortization
Balances subject to amortization	$ 0	$ 0

Balances not subject to amortisation.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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-Name Accounting Standards Codification
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Carrying amount of finite-lived intangible assets, indefinite-lived intangible assets and goodwill. Goodwill is an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. Intangible assets are assets, not including financial assets, lacking physical substance.

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Amount after accumulated amortization of finite-lived and indefinite-lived intangible assets classified as other.

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