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	Jun. 30, 2013	Dec. 31, 2012
MetroCorp Bancshares Inc [Member]
Total risk-based capital ratio
Actual Amount (in Dollars)	$ 217,914	$ 212,083
Actual Ratio	17.10%	17.95%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	101,953	94,509
Minimum Required For Capital Adequacy Purposes Ratio	8.00%	8.00%
Tier 1 risk-based capital ratio
Actual Amount (in Dollars)	201,902	197,077
Actual Ratio	15.84%	16.68%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	50,977	47,255
Minimum Required For Capital Adequacy Purposes Ratio	4.00%	4.00%
Leverage ratio
Actual Amount (in Dollars)	201,902	197,077
Actual Ratio	12.87%	13.18%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	62,743	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)	149,083	152,613
Actual Ratio	16.07%	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)	137,437	141,702
Actual Ratio	14.82%	16.53%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	37,100	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)	137,437	141,702
Actual Ratio	12.09%	12.70%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	45,479	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)	56,848	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)	54,222	52,714
Actual Ratio	15.73%	16.34%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	27,582	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)	34,477	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)	49,882	48,636
Actual Ratio	14.47%	15.07%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	13,791	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)	20,686	19,360
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	6.00%	6.00%
Leverage ratio
Actual Amount (in Dollars)	49,882	48,636
Actual Ratio	11.55%	12.76%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	17,273	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)	$ 21,591	$ 19,053
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	5.00%	5.00%