REGULATORY CAPITAL (Summary of actual capital amounts and ratios) (Details) $ in Thousands	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital (to risk-weighted assets), Actual Amount	$ 410,959	$ 350,403
Total capital (to risk-weighted assets), Actual Ratio	12.7	12.5
Total capital (to risk-weighted assets), For Capital Adequacy Amount	$ 257,941
Total capital (to risk-weighted assets), For Capital Adequacy Ratio	8.0
Tier 1 common equity (to risk-weighted assets), Actual Amount	$ 324,592	$ 282,646
Tier 1 common equity (to risk-weighted assets), Actual Ratio	10.1	10.1
Tier 1 common equity (to risk-weighted assets), For Capital Adequacy Amount	$ 145,092
Tier 1 common equity (to risk-weighted assets), For Capital Adequacy Ratio	4.50%
Tier 1 capital (to risk-weighted assets), Actual Amount	$ 350,714	$ 308,769
Tier 1 capital (to risk-weighted assets), Actual Ratio	10.9	11.0
Tier 1 capital (to risk-weighted assets), For Capital Adequacy Amount	$ 193,456
Tier 1 capital (to risk-weighted assets), For Capital Adequacy Ratio	6.0
Tier 1 capital (to average assets), Actual Amount	$ 350,714	$ 308,769
Tier 1 capital (to average assets), Actual Ratio	8.5	9.4
Tier 1 capital (to average assets), For Capital Adequacy Amount	$ 165,767
Tier 1 capital (to average assets), For Capital Adequacy Ratio	4.0
Total capital (to risk-weighted assets), Minimum for Capital Adequacy plus Capital Conservation Buffer Amount		$ 223,973
Total capital (to risk-weighted assets), Minimum for Capital Adequacy plus Capital Conservation Buffer Ratio		8.00%
Tier 1 common equity (to risk-weighted assets), Minimum for Capital Adequacy plus Capital Conservation Buffer Amount		$ 125,985
Tier 1 common equity (to risk-weighted assets), Minimum for Capital Adequacy plus Capital Conservation Buffer Ratio		4.50%
Tier 1 capital (to risk-weighted assets), Minimum for Capital Adequacy plus Capital Conservation Buffer Amount		$ 167,980
Tier 1 capital (to risk-weighted assets), Minimum for Capital Adequacy plus Capital Conservation Buffer Ratio		6.00%
Tier 1 capital (to average assets), Minimum for Capital Adequacy plus Capital Conservation Buffer Amount		$ 131,087
Tier 1 capital (to average assets), Minimum for Capital Adequacy plus Capital Conservation Buffer Ratio		4.00%
Metropolitan Commercial Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital (to risk-weighted assets), Actual Amount	$ 410,295	$ 356,353
Total capital (to risk-weighted assets), Actual Ratio	12.7	12.7
Total capital (to risk-weighted assets), For Capital Adequacy Amount	$ 257,827	$ 223,858
Total capital (to risk-weighted assets), For Capital Adequacy Ratio	8.0	8.0
Total capital (to risk-weighted assets), To be Well Capitalized under Prompt Corrective Action Regulations Amount	$ 322,284	$ 279,823
Total capital (to risk-weighted assets), To be Well Capitalized under Prompt Corrective Action Regulations Ratio	10.0	10.0
Tier 1 common equity (to risk-weighted assets), Actual Amount	$ 374,712	$ 329,905
Tier 1 common equity (to risk-weighted assets), Actual Ratio	11.6	11.8
Tier 1 common equity (to risk-weighted assets), For Capital Adequacy Amount	$ 145,028	$ 125,920
Tier 1 common equity (to risk-weighted assets), For Capital Adequacy Ratio	4.50%	4.50%
Tier 1 common equity (to risk-weighted assets), To be Well Capitalized under Prompt Corrective Action Regulations Amount	$ 209,485	$ 181,885
Tier 1 common equity (to risk-weighted assets), To be Well Capitalized under Prompt Corrective Action Regulations Ratio	6.50%	6.50%
Tier 1 capital (to risk-weighted assets), Actual Amount	$ 374,712	$ 329,905
Tier 1 capital (to risk-weighted assets), Actual Ratio	11.6	11.8
Tier 1 capital (to risk-weighted assets), For Capital Adequacy Amount	$ 193,370	$ 167,894
Tier 1 capital (to risk-weighted assets), For Capital Adequacy Ratio	6.0	6.0
Tier 1 capital (to risk-weighted assets), To be Well Capitalized under Prompt Corrective Action Regulations Amount	$ 257,827	$ 223,858
Tier 1 capital (to risk-weighted assets), To be Well Capitalized under Prompt Corrective Action Regulations Ratio	8.0	8.0
Tier 1 capital (to average assets), Actual Amount	$ 374,712	$ 329,905
Tier 1 capital (to average assets), Actual Ratio	9.0	10.1
Tier 1 capital (to average assets), For Capital Adequacy Amount	$ 165,704	$ 131,000
Tier 1 capital (to average assets), For Capital Adequacy Ratio	4.0	4.0
Tier 1 capital (to average assets), To be Well Capitalized under Prompt Corrective Action Regulations Amount	$ 207,130	$ 163,750
Tier 1 capital (to average assets), To be Well Capitalized under Prompt Corrective Action Regulations Ratio	5.0	5.0