Note 8 - Regulatory Matters (Detail) - Comparison Of The Company’s And Each Of The Banks’ Leverage And Risk-Weighted Capital Ratios (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
MetroCorp Bancshares Inc [Member]
Tier 1 risk-based capital ratio
Actual Amount (in Dollars)	$ 192,867	$ 181,368
Actual Ratio	16.41%	16.02%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	47,014	45,276
Minimum Required For Capital Adequacy Purposes Ratio	4.00%	4.00%
MetroBank NA [Member]
Tier 1 risk-based capital ratio
Actual Amount (in Dollars)	141,082	129,864
Actual Ratio	16.35%	15.55%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	34,510	33,416
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)	51,764	50,124
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	6.00%	6.00%
Leverage ratio
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	51,764	50,124
Metro United Bank [Member]
Tier 1 risk-based capital ratio
Actual Amount (in Dollars)	47,093	45,034
Actual Ratio	15.22%	15.22%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	12,376	11,837
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)	18,564	17,756
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	6.00%	6.00%
Leverage ratio
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	18,564	17,756
MetroCorp Bancshares Inc [Member]
Tier 1 risk-based capital ratio
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Amount (in Dollars)	59,824	59,659
Leverage ratio
Actual Amount (in Dollars)	192,867	181,368
Actual Ratio	12.90%	12.16%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	59,824	59,659
Minimum Required For Capital Adequacy Purposes Ratio	4.00%	4.00%
MetroBank NA [Member]
Tier 1 risk-based capital ratio
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Amount (in Dollars)	44,720	44,514
Leverage ratio
Actual Amount (in Dollars)	141,082	129,864
Actual Ratio	12.62%	11.67%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	44,720	44,514
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)	55,900	55,643
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	5.00%	5.00%
Metro United Bank [Member]
Tier 1 risk-based capital ratio
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Amount (in Dollars)	15,095	15,269
Leverage ratio
Actual Amount (in Dollars)	47,093	45,034
Actual Ratio	12.48%	11.80%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	15,095	15,269
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)	18,869	19,086
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	5.00%	5.00%
MetroCorp Bancshares Inc [Member]
Total risk-based capital ratio
Actual Amount (in Dollars)	207,884	195,765
Actual Ratio	17.69%	17.30%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	94,029	90,552
Minimum Required For Capital Adequacy Purposes Ratio	8.00%	8.00%
MetroBank NA [Member]
Total risk-based capital ratio
Actual Amount (in Dollars)	152,149	140,510
Actual Ratio	17.64%	16.82%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	69,019	66,831
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)	86,274	83,539
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	10.00%	10.00%
Metro United Bank [Member]
Total risk-based capital ratio
Actual Amount (in Dollars)	51,004	48,778
Actual Ratio	16.49%	16.48%
Minimum Required For Capital Adequacy Purposes Amount (in Dollars)	24,752	23,674
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)	$ 30,940	$ 29,593
To be Categorized as Well Capitalized under Prompt Corrective Action Provisions Ratio	10.00%	10.00%