| **Goodwill and Other Amortizing Intangible Assets - Additional Information (Detail) (USD $)** | 12 Months Ended |               |
|-----------------------------------------------------------------------------------------------|-----------------|---------------|
||
| **Goodwill And Other Intangibles [Line Items]**                                               |            |          |   |   |
| Goodwill                                                                                      | $ 159,956,000   | $ 159,956,000 |   |   |
| Impairment charges on goodwill                                                                | 0               | 0             | 0 |   |
| Fair value of goodwill above book value                                                       |            |          |   | 30.00% |
| Amortization of other intangible assets                                                       | $ 1,064,000     | $ 1,467,000   | $ 1,534,000 |   |
| Core Deposits Intangibles [Member]                                                            |            |          |   |   |
| **Goodwill And Other Intangibles [Line Items]**                                               |            |          |   |   |
| Core deposits remaining amortization period                                                   | 6 years         |          |   |   |
| Core deposits weighted average amortization period                                            | 2 years         |          |   |   |

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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Finite Lived Intangible Asset Remaining Amortization Period
+ References
No definition available.
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| - Definition
Intangibles Weighted Average Amortization Period
+ References
No definition available.
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| - Definition
Percentage Of Fair Value Of Goodwill Above Book Value
+ References
No definition available.
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| - Definition
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.
+ References
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| - Definition
Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.
+ References
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| - Definition
Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.
+ References
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