REGULATORY MATTERS, COMMITMENTS AND CONTINGENCIES - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Commitments To Extent Credit	$ 1,100.0
Credit Cards [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Commitments To Extent Credit	663.4
Commercial And Financial Standby Letters Of Credit [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Commitments To Extent Credit	$ 45.1
Basel III [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Common Equity Tier 1 Capital Conservation Buffer	2.50%
Basel III [Member] \| Minimum [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Common Equity Tier1 Capital To Risk Weight Assets Ratio	4.50%
Common Equity Tier 1 Capital To Risk Weight Assets Ratio Plus Common Equity Tier 1 Capital Conservation Buffer	7.00%
Total Tier 1 Capital To Risk Weight Assets Ratio	6.00%
Total Tier 1 Capital To Risk Weight Assets Ratio Plus Common Equity Tier 1 Capital Conservation Buffer	8.50%
Total Tier 1 Capital And Tier 2 Capital To Risk Weight Assets Ratio	8.00%
Total Tier 1 Capital And Tier 2 Capital To Risk Weight Assets Ratio Plus Common Equity Tier 1 Capital Conservation Buffer	10.50%
Leverage Ratio	4.00%
Common Equity Tier 1 Capital Conservation Buffer First Year	0.625%
FirstBank [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Leverage ratio	15.34%	15.10%
Tier 1 risk based capital ratio	20.44%	19.53%
Total Risk Based Capital Ratio	21.71%	20.80%
Tier 1 risk based capital ratio to be considered well capitalzed under PCA	8.00%	8.00%
Total risk based capital to be considered well capitalized under PCA	10.00%	10.00%
Leverage ratio to be considered well capitalized under PCA	5.00%	5.00%
Common Equity Tier1 Capital To Risk Weight Assets Ratio	17.36%	16.92%

Amount represents legally binding commitments to extend credit to a counterparty under certain terms and conditions.

No definition available.

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- Definition

The percentage by which the company's Common Equity Tier 1 Risk Based Capital must exceeds the minimum required for no restrictions.

+ References

No definition available.

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- Definition

The percentage by which the company's Common Equity Tier 1 Risk Based Capital must exceeds the minimum required for no restrictions in the first year of transition period under Basel III rule.

+ References

No definition available.

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- Definition

Common Equity Tier 1 capital divided by risk weighted assets as defined by new Basel III rule.

+ References

No definition available.

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- Definition

Minimun common equity tier 1 capital to risk weight assets for capital adequacy purposes plus capital conservation buffer as required by Basel III rule.

+ References

No definition available.

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- Definition

Minimum Tier 1 capital to average assets for capital adequacy purposes as required by Basel III rule.

+ References

No definition available.

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- Definition

New total tier 1 capital plus tier 2 capital to risk weight assets ratio introduced by Basel III rules.

+ References

No definition available.

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- Definition

Minimun Total capital to risk weight assets for capital adequacy purposes plus capital conservation buffer as required by Basel III rule.

+ References

No definition available.

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- Definition

Minimum Tier 1 capital divided by risk weighted assets for capital adequacy purposes as defined by new Basel III rule.

+ References

No definition available.

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- Definition

Minimun Tier 1 capital to risk weight assets for capital adequacy purposes plus capital conservation buffer as required by Basel III rule.

+ References

No definition available.

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- Definition

The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

+ References

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826

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- 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.

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- Definition

The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action.

+ References

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- Definition

Tier 1 Leverage Capital divided by average assets as defined in the regulations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826

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- Definition

The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action.

+ References

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- Definition

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

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