REGULATORY MATTERS, COMMITMENTS AND CONTINGENCIES - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016	Mar. 31, 2016
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
FDIC Deposits Insurance Assesment Surcharge			$ 0.045
Commitments To Extent Credit	$ 1,200,000,000
Credit Cards [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Commitments To Extent Credit	681,300,000
Commercial And Financial Standby Letters Of Credit [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Commitments To Extent Credit	$ 38,300,000
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	15.53%	15.10%
Tier 1 risk based capital ratio	20.43%	19.53%
Total Risk Based Capital Ratio	21.70%	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	17.37%	16.92%