Regulatory Matters - Additional Information (Detail) - USD ($)	Dec. 31, 2018	Jan. 01, 2015
Regulatory Matters [Line Items]
Total risk-based capital ratio, Actual Ratio	8.00%
Tier 1 risk-based capital ratio, Actual Ratio	4.00%
Basel III [Member]
Regulatory Matters [Line Items]
Leverage capital ratio		3.00%
Basel III [Member] \| Criteria 1 [Member]
Regulatory Matters [Line Items]
Total risk-based capital ratio, Actual Ratio	10.50%
Tier 1 risk-based capital ratio, Actual Ratio	8.50%
Common Equity tier 1 capital ratio, Actual Ratio	7.00%
Basel III [Member] \| Criteria 2 [Member]
Regulatory Matters [Line Items]
Total risk-based capital ratio, Actual Ratio	10.00%
Tier 1 risk-based capital ratio, Actual Ratio	8.00%
Common Equity tier 1 capital ratio, Actual Ratio	6.50%
Leverage capital ratio	5.00%
Minimum [Member] \| Basel III [Member]
Regulatory Matters [Line Items]
Total risk-based capital ratio, Actual Ratio		8.00%
Tier 1 risk-based capital ratio, Actual Ratio		4.00%
Consolidated risk weighted asset	$ 500,000,000
Minimum [Member] \| Basel III [Member] \| Criteria 1 [Member]
Regulatory Matters [Line Items]
Common Equity tier 1 capital ratio, Actual Ratio	2.50%
Maximum [Member] \| Basel III [Member]
Regulatory Matters [Line Items]
Tier 1 risk-based capital ratio, Actual Ratio		6.00%
Common Equity tier 1 capital ratio, Actual Ratio		4.50%
Leverage capital ratio		4.00%

Common equity tier one capital to risk weighted assets.

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Leverage capital ratio.

+ References

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Regulatory Matters [Line Items]

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- Definition

Total Capital divided by risk weighted assets as defined in the regulations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

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Amount of risk-weighted assets as calculated in accordance with U.S. Federal regulatory capital standards.

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- Definition

Tier 1 capital divided by risk weighted assets as defined by regulations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

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