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Intangible Assets and Goodwill - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Weighted-average life	6 years 8 months 12 days
Customer Related Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average life	5 years 1 month 6 days
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average life	6 years 10 months 24 days
Mortgage Servicing Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average life	2 years

X

- Definition

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.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: