Note 4 - Loans and Allowance for Credit Losses (Detail) - Impaired loans (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Commercial [Member]
Impaired loans with no related allowance recorded:
Impaired loans with no related allowance recorded, recorded investment	$ 2,277	$ 3,100
Impaired loans with no related allowance recorded, unpaid principal balance	8,187	9,506
Impaired loans with an allowance recorded:
Impaired loans with an allowance recorded, recorded investment	9,952	12,129
Impaired loans with an allowance recorded, unpaid principal balance	11,582	13,739
Impaired loans with an allowance recorded, related allowance	1,609	2,588
Total:
Recorded Investment	12,229	15,229
Unpaid Principal Balance	19,769	23,245
Related Allowance	1,609	2,588
Commercial Real Estate Loans [Member]
Impaired loans with no related allowance recorded:
Impaired loans with no related allowance recorded, recorded investment	26,155	24,135
Impaired loans with no related allowance recorded, unpaid principal balance	30,081	27,972
Impaired loans with an allowance recorded:
Impaired loans with an allowance recorded, recorded investment	2,686	4,038
Impaired loans with an allowance recorded, unpaid principal balance	2,686	4,038
Impaired loans with an allowance recorded, related allowance	584	164
Total:
Recorded Investment	28,841	28,173
Unpaid Principal Balance	32,767	32,010
Related Allowance	584	164
Construction [Member]
Impaired loans with no related allowance recorded:
Impaired loans with no related allowance recorded, recorded investment	1,859	2,363
Impaired loans with no related allowance recorded, unpaid principal balance	2,355	2,992
Total:
Recorded Investment	1,859	2,363
Unpaid Principal Balance	2,355	2,992
Residential Real Estate Loans [Member]
Impaired loans with no related allowance recorded:
Impaired loans with no related allowance recorded, recorded investment	701	668
Impaired loans with no related allowance recorded, unpaid principal balance	702	668
Total:
Recorded Investment	701	668
Unpaid Principal Balance	702	668
Consumer Installment And Other [Member]
Impaired loans with no related allowance recorded:
Impaired loans with no related allowance recorded, recorded investment	1,597	2,328
Impaired loans with no related allowance recorded, unpaid principal balance	2,402	2,616
Total:
Recorded Investment	1,597	2,328
Unpaid Principal Balance	$ 2,402	$ 2,616