Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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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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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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GOODWILL AND OTHER INTANGIBLE ASSETS, NET - Additional Information (Detail) - USD ($)		3 Months Ended			9 Months Ended
	Aug. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Goodwill		$ 37,144,000			$ 37,144,000		$ 37,144,000
Goodwill write-off	$ 0
Aggregate amortization expense		$ 693,000	$ 916,000		$ 2,363,000	$ 3,062,000
Trade name intangibles
Finite-Lived Intangible Assets [Line Items]
Intangible asset write-off				$ 90,000
Core deposit intangibles
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period					5 years 6 months 7 days
Core deposit intangibles \| Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period of other intangible assets					4 years
Core deposit intangibles \| Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization period of other intangible assets					10 years
Customer relationship intangible
Finite-Lived Intangible Assets [Line Items]
Intangible asset write-off				246,000
Commercial Banking
Finite-Lived Intangible Assets [Line Items]
Goodwill								$ 37,100,000
Mortgage Banking
Finite-Lived Intangible Assets [Line Items]
Goodwill								$ 2,100,000
Goodwill write-off				$ 2,100,000