Note 8 - Fair Value Measurement (Detail) - Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Impaired loans, net of specific reserves--
Current Period Gains (Losses)	$ (45)	$ (318)	$ (501)
Commercial and Industrial Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Impaired loans, net of specific reserves--
Fair Value	97	582	1,969
Commercial and Industrial Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Impaired loans, net of specific reserves--
Fair Value	97	582	1,969
Commercial and Industrial Loans [Member]
Impaired loans, net of specific reserves--
Current Period Gains (Losses)	(83)		7
Residential Real Estate Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Impaired loans, net of specific reserves--
Fair Value	496	61	570
Residential Real Estate Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Impaired loans, net of specific reserves--
Fair Value	496	61	570
Residential Real Estate Loans [Member]
Impaired loans, net of specific reserves--
Current Period Gains (Losses)	4		(324)
Commercial Real Estate Owner Occupied [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Impaired loans, net of specific reserves--
Fair Value	1,423	1,571	2,232
Commercial Real Estate Owner Occupied [Member] | Fair Value, Measurements, Nonrecurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Impaired loans, net of specific reserves--
Fair Value	1,423	1,571	2,232
Commercial Real Estate Owner Occupied [Member]
Impaired loans, net of specific reserves--
Current Period Gains (Losses)	19		(20)
Commercial Real Estate Non Owner Occupied [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Impaired loans, net of specific reserves--
Fair Value	0
Commercial Real Estate Non Owner Occupied [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Impaired loans, net of specific reserves--
Fair Value	0
Commercial Real Estate Non Owner Occupied [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Impaired loans, net of specific reserves--
Fair Value	679		683
Commercial Real Estate Non Owner Occupied [Member] | Fair Value, Measurements, Nonrecurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Impaired loans, net of specific reserves--
Fair Value	679		683
Commercial Real Estate Non Owner Occupied [Member]
Impaired loans, net of specific reserves--
Current Period Gains (Losses)	12	(128)	(66)
All Other Real Estate Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Impaired loans, net of specific reserves--
Fair Value		0
All Other Real Estate Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Impaired loans, net of specific reserves--
Fair Value		0
All Other Real Estate Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Impaired loans, net of specific reserves--
Fair Value	24	0	27
All Other Real Estate Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Impaired loans, net of specific reserves--
Fair Value	24	0	27
All Other Real Estate Loans [Member]
Impaired loans, net of specific reserves--
Current Period Gains (Losses)	1	0	(2)
Construction and Land Development Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Impaired loans, net of specific reserves--
Fair Value	201		452
Construction and Land Development Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Impaired loans, net of specific reserves--
Fair Value	201		452
Construction and Land Development Loans [Member]
Impaired loans, net of specific reserves--
Current Period Gains (Losses)	2	(190)	(96)
Other Real Estate Owned (Member) | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Non-financial assets measured at fair value on a non-recurring basis:
Fair Value	818	2,224	818
Other Real Estate Owned (Member) | Fair Value, Measurements, Nonrecurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Non-financial assets measured at fair value on a non-recurring basis:
Fair Value	818	2,224	818
Other Real Estate Owned (Member)
Non-financial assets measured at fair value on a non-recurring basis:
Current Period Gains (Losses)		(358)	(463)
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Impaired loans, net of specific reserves--
Fair Value	2,920	2,214	5,933
Fair Value, Measurements, Nonrecurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Impaired loans, net of specific reserves--
Fair Value	$ 2,920	$ 2,214	$ 5,933