Note 7 - Regulatory Matters (Details) - Comparison Of The Company’s And Each Of The Banks’ Leverage And Risk-Weighted Capital Ratios (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
MetroCorp Bancshares Inc [Member]
Total risk-based capital ratio
Actual Amount (in Dollars)	$ 221,088	$ 212,083
Actual Ratio	17.22%	17.95%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	102,719	94,509
Minimum Required For Capital Adequacy Purposes Ratio	8.00%	8.00%
Tier 1 risk-based capital ratio
Actual Amount (in Dollars)	204,969	197,077
Actual Ratio	15.96%	16.68%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	51,359	47,255
Minimum Required For Capital Adequacy Purposes Ratio	4.00%	4.00%
Leverage ratio
Actual Amount (in Dollars)	204,969	197,077
Actual Ratio	12.85%	13.18%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	63,801	59,812
Minimum Required For Capital Adequacy Purposes Ratio	4.00%	4.00%
MetroBank NA [Member]
Total risk-based capital ratio
Actual Amount (in Dollars)	152,143	152,613
Actual Ratio	16.40%	17.80%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	74,199	68,587
Minimum Required For Capital Adequacy Purposes Ratio	8.00%	8.00%
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Amount (in Dollars)	92,749	85,734
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	10.00%	10.00%
Tier 1 risk-based capital ratio
Actual Amount (in Dollars)	140,511	141,702
Actual Ratio	15.15%	16.53%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	37,099	34,293
Minimum Required For Capital Adequacy Purposes Ratio	4.00%	4.00%
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Amount (in Dollars)	55,649	51,440
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	6.00%	6.00%
Leverage ratio
Actual Amount (in Dollars)	140,511	141,702
Actual Ratio	12.33%	12.70%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	45,587	44,613
Minimum Required For Capital Adequacy Purposes Ratio	4.00%	4.00%
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Amount (in Dollars)	56,984	55,766
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	5.00%	5.00%
Metro United [Member]
Total risk-based capital ratio
Actual Amount (in Dollars)	55,536	52,714
Actual Ratio	15.67%	16.34%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	28,351	25,814
Minimum Required For Capital Adequacy Purposes Ratio	8.00%	8.00%
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Amount (in Dollars)	35,439	32,267
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	10.00%	10.00%
Tier 1 risk-based capital ratio
Actual Amount (in Dollars)	51,076	48,636
Actual Ratio	14.41%	15.07%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	14,176	12,907
Minimum Required For Capital Adequacy Purposes Ratio	4.00%	4.00%
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Amount (in Dollars)	21,263	19,360
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	6.00%	6.00%
Leverage ratio
Actual Amount (in Dollars)	51,076	48,636
Actual Ratio	11.16%	12.76%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	18,299	15,243
Minimum Required For Capital Adequacy Purposes Ratio	4.00%	4.00%
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Amount (in Dollars)	$ 22,873	$ 19,053
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	5.00%	5.00%