REGULATORY MATTERS, COMMITMENTS AND CONTINGENCIES - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Threshold For Deposits Insurance Assesment Surcharge			$ 10,000,000,000
FDIC Deposits Insurance Assesment Surcharge			0.045
Deposits Insurance Surcharge Assesment Base			$ 100
Commitments To Extent Credit	$ 1,100,000,000	$ 1,100,000,000
Decrease Increase Federal Deposit Insurance Corporation Premium Expense	800,000
Credit Cards [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Commitments To Extent Credit	631,500,000	631,500,000
Commercial And Financial Standby Letters Of Credit [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Commitments To Extent Credit	$ 46,700,000	$ 46,700,000
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%	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	14.40%	14.40%		13.33%
Tier 1 risk based capital ratio	19.46%	19.46%		18.45%
Total Risk Based Capital Ratio	20.73%	20.73%		19.73%
Tier 1 risk based capital ratio to be considered well capitalzed under PCA	8.00%	8.00%		8.00%
Total risk based capital to be considered well capitalized under PCA	10.00%	10.00%		10.00%
Leverage ratio to be considered well capitalized under PCA	5.00%	5.00%		5.00%
Common Equity Tier1 Capital To Risk Weight Assets Ratio	16.83%	16.83%		16.35%