REGULATORY MATTERS - Company's and Bank's Actual Capital Amounts and Ratios (Details) $ in Thousands	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Company
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Leverage Ratio (tier 1 capital to average assets) Actual Amount	$ 1,897,725	$ 1,701,997
Tier 1 Leverage Ratio (tier 1 capital to average assets) Actual Ratio	0.0863	0.0899
Tier 1 Leverage Ratio (tier 1 capital to average assets) For Capital Adequacy Purposes Amount	$ 879,079	$ 757,195
Tier 1 Leverage Ratio (tier 1 capital to average assets) For Capital Adequacy Purposes Ratio	0.0400	0.0400
CET1 Ratio (common equity tier 1 capital to risk weighted assets) Actual Amount	$ 1,897,725	$ 1,701,997
CET1 Ratio (common equity tier 1 capital to risk weighted assets) Actual Ratio	10.46%	11.14%
CET1 Ratio (common equity tier 1 capital to risk weighted assets) Adequacy Purposes Amount	$ 1,270,535	$ 1,069,425
CET1 Ratio (common equity tier 1 capital to risk weighted assets) Adequacy Purposes Ratio	7.00%	7.00%
Tier 1 Capital Ratio (tier 1 capital to risk weighted assets) Actual Amount	$ 1,897,725	$ 1,701,997
Tier 1 Capital Ratio (tier 1 capital to risk weighted assets) Actual Ratio	0.1046	0.1114
Tier 1 Capital Ratio (tier 1 capital to risk weighted assets) For Capital Adequacy Purposes Amount	$ 1,542,792	$ 1,298,588
Tier 1 Capital Ratio (tier 1 capital to risk weighted assets) For Capital Adequacy Purposes Ratio	0.0850	0.0850
Total Capital Ratio (total capital to risk weighted assets) Actual Amount	$ 2,500,287	$ 2,332,385
Total Capital Ratio (total capital to risk weighted assets) Actual Ratio	0.1378	0.1527
Total Capital Ratio (total capital to risk weighted assets) For Capital Adequacy Purposes Amount	$ 1,905,802	$ 1,604,138
Total Capital Ratio (total capital to risk weighted assets) For Capital Adequacy Purposes Ratio	0.1050	0.1050
Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Leverage Ratio (tier 1 capital to average assets) Actual Amount	$ 2,084,465	$ 1,964,717
Tier 1 Leverage Ratio (tier 1 capital to average assets) Actual Ratio	0.0950	0.1039
Tier 1 Leverage Ratio (tier 1 capital to average assets) For Capital Adequacy Purposes Amount	$ 877,891	$ 756,510
Tier 1 Leverage Ratio (tier 1 capital to average assets) For Capital Adequacy Purposes Ratio	0.0400	0.0400
Tier 1 Leverage Ratio (tier 1 capital to average assets) To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 1,097,364	$ 945,637
Tier 1 Leverage Ratio (tier 1 capital to average assets) To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	0.0500	0.0500
CET1 Ratio (common equity tier 1 capital to risk weighted assets) Actual Amount	$ 2,084,465	$ 1,964,717
CET1 Ratio (common equity tier 1 capital to risk weighted assets) Actual Ratio	11.50%	12.87%
CET1 Ratio (common equity tier 1 capital to risk weighted assets) Adequacy Purposes Amount	$ 1,268,622	$ 1,068,756
CET1 Ratio (common equity tier 1 capital to risk weighted assets) Adequacy Purposes Ratio	7.00%	7.00%
CET1 Ratio (common equity tier 1 capital to risk weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 1,178,007	$ 992,417
CET1 Ratio (common equity tier 1 capital to risk weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	6.50%	6.50%
Tier 1 Capital Ratio (tier 1 capital to risk weighted assets) Actual Amount	$ 2,084,465	$ 1,964,717
Tier 1 Capital Ratio (tier 1 capital to risk weighted assets) Actual Ratio	0.1150	0.1287
Tier 1 Capital Ratio (tier 1 capital to risk weighted assets) For Capital Adequacy Purposes Amount	$ 1,540,470	$ 1,297,775
Tier 1 Capital Ratio (tier 1 capital to risk weighted assets) For Capital Adequacy Purposes Ratio	0.0850	0.0850
Tier 1 Capital Ratio (tier 1 capital to risk weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 1,449,854	$ 1,221,436
Tier 1 Capital Ratio (tier 1 capital to risk weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	0.0800	0.0800
Total Capital Ratio (total capital to risk weighted assets) Actual Amount	$ 2,255,699	$ 2,165,760
Total Capital Ratio (total capital to risk weighted assets) Actual Ratio	0.1245	0.1419
Total Capital Ratio (total capital to risk weighted assets) For Capital Adequacy Purposes Amount	$ 1,902,934	$ 1,603,134
Total Capital Ratio (total capital to risk weighted assets) For Capital Adequacy Purposes Ratio	0.1050	0.1050
Total Capital Ratio (total capital to risk weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 1,812,318	$ 1,526,795
Total Capital Ratio (total capital to risk weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	0.1000	0.1000

Common Equity Tier 1 Risk Based Capital as defined in the regulations.

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Common equity tier one risk based capital required for capital adequacy to risk weighted assets.

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

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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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