REGULATORY MATTERS - Schedule of Capital and Capital Ratios (Details) $ in Thousands	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
FFI
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
CET1 capital ratio, Actual Amount	$ 846,515	$ 589,276
Tier 1 leverage/(core) ratio, Actual Amount	846,515	589,276
Tier 1 risk-based capital ratio, Actual Amount	846,515	589,276
Total risk-based capital ratio, Actual Amount	$ 887,821	$ 620,700
CET1 capital ratio, Actual Ratio	0.1134	0.1155
Tier 1 leverage/(core) ratio, Actual Ratio	0.0843	0.0893
Tier 1 risk-based capital ratio, Actual Ratio	0.1134	0.1155
Total risk-based capital ratio, Actual Ratio	0.1190	0.1217
CET1 capital ratio, For Capital Adequacy Purposes Amount	$ 335,801	$ 229,490
Tier 1 leverage/(core) ratio, For Capital Adequacy Purposes Amount	401,645	263,986
Tier 1 risk-based capital ratio, For Capital Adequacy Purposes Amount	447,735	305,987
Total risk-based capital ratio, For Capital Adequacy Purposes Amount	$ 596,980	$ 407,982
CET1 capital ratio, For Capital Adequacy Purposes Ratio	0.0450	0.0450
Tier 1 leverage/(core) ratio, For Capital Adequacy Purposes Ratio	0.0400	0.0400
Tier 1 risk-based capital ratio, For Capital Adequacy Purposes Ratio	0.0600	0.0600
Total risk-based capital ratio, For Capital Adequacy Purposes Ratio	0.0800	0.0800
FFA
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
CET1 capital ratio, Actual Amount	$ 854,075	$ 591,171
Tier 1 leverage/(core) ratio, Actual Amount	854,075	591,171
Tier 1 risk-based capital ratio, Actual Amount	854,075	591,171
Total risk-based capital ratio, Actual Amount	$ 895,381	$ 622,595
CET1 capital ratio, Actual Ratio	0.1149	0.1163
Tier 1 leverage/(core) ratio, Actual Ratio	0.0853	0.0898
Tier 1 risk-based capital ratio, Actual Ratio	0.1149	0.1163
Total risk-based capital ratio, Actual Ratio	0.1204	0.1225
CET1 capital ratio, For Capital Adequacy Purposes Amount	$ 334,608	$ 228,703
Tier 1 leverage/(core) ratio, For Capital Adequacy Purposes Amount	400,616	263,330
Tier 1 risk-based capital ratio, For Capital Adequacy Purposes Amount	446,144	304,938
Total risk-based capital ratio, For Capital Adequacy Purposes Amount	$ 594,859	$ 406,583
CET1 capital ratio, For Capital Adequacy Purposes Ratio	0.0450	0.0450
Tier 1 leverage/(core) ratio, For Capital Adequacy Purposes Ratio	0.0400	0.0400
Tier 1 risk-based capital ratio, For Capital Adequacy Purposes Ratio	0.0600	0.0600
Total risk-based capital ratio, For Capital Adequacy Purposes Ratio	0.0800	0.0800
CET1 capital ratio, To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	$ 483,323	$ 330,349
Tier 1 leverage/(core) ratio, To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	500,770	329,162
Tier 1 risk-based capital ratio, To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	594,859	406,583
Total risk-based capital ratio, To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	$ 743,574	$ 508,229
CET1 leverage ratio, To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio	0.0650	0.0650
Tier 1 leverage/(core) ratio, To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio	0.0500	0.0500
Tier 1 risk-based capital ratio, To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio	0.0800	0.0800
Total risk-based capital ratio, To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio	0.1000	0.1000

Common equity tier 1 capital, for capital adequacy purposes, ratio.

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Common equity tier one capital required to be well capitalized, ratio.

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Amount of total capital as defined by regulatory framework.

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Amount of minimum total risk-based capital required for capital adequacy as defined by regulatory framework.

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Ratio of minimum total risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

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Amount of Tier 1 leverage capital as defined by regulatory framework.

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