Note 4 - Loans and Allowance for Credit Losses (Detail) - Recorded investment in loans evaluated for impairment (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012
Allowance for credit losses:
Individually evaluated for impairment	$ 2,193		$ 2,752
Collectively evaluated for impairment	30,854		30,175
Total	33,047		32,927		34,576
Carrying value of loans:
Individually evaluated for impairment	26,772		29,023
Collectively evaluated for impairment	1,996,621		2,067,705
Purchased loans with evidence of credit deterioration	13,541		14,629
Total	2,036,934		2,111,357
Commercial [Member]
Allowance for credit losses:
Individually evaluated for impairment	886		1,865
Collectively evaluated for impairment	6,313		6,314
Total	7,199		8,179		8,457
Carrying value of loans:
Individually evaluated for impairment	2,171		5,153
Collectively evaluated for impairment	316,331		334,963
Total	318,502		340,116
Commercial Real Estate Loans [Member]
Allowance for credit losses:
Individually evaluated for impairment	584		134
Collectively evaluated for impairment	10,384		9,938
Total	10,968		10,072		11,427
Carrying value of loans:
Individually evaluated for impairment	3,319		4,161
Collectively evaluated for impairment	621,866		628,766
Total	625,185		632,927
Construction [Member]
Allowance for credit losses:
Collectively evaluated for impairment	480		484
Total	480		484		2,781
Carrying value of loans:
Collectively evaluated for impairment	7,920		7,984
Total	7,920		7,984
Residential Real Estate Loans [Member]
Allowance for credit losses:
Collectively evaluated for impairment	539		380
Total	539		380		645
Carrying value of loans:
Collectively evaluated for impairment	213,919		222,458
Total	213,919		222,458
Consumer Installment And Other [Member]
Allowance for credit losses:
Collectively evaluated for impairment	3,221		3,613
Total	3,221		3,613		3,014
Carrying value of loans:
Collectively evaluated for impairment	447,870		460,698
Total	447,870		460,698
Purchased Non-Covered Loans [Member]
Carrying value of loans:
Individually evaluated for impairment	5,196		3,029
Collectively evaluated for impairment	59,348		65,098
Purchased loans with evidence of credit deterioration	5,960		6,764
Total	70,504		74,891
Purchased Covered Loans [Member]
Allowance for credit losses:
Individually evaluated for impairment	723		753
Collectively evaluated for impairment	15		252
Total	738		1,005		139
Carrying value of loans:
Individually evaluated for impairment	16,086		16,680
Collectively evaluated for impairment	329,367		347,738
Purchased loans with evidence of credit deterioration	7,581		7,865
Total	353,034	[1]	372,283	[1]
Unallocated Financing Receivable [Member]
Allowance for credit losses:
Collectively evaluated for impairment	9,902		9,194
Total	$ 9,902		$ 9,194		$ 8,113

[1] Credit risk profile reflects internally assigned grade of purchased covered loans without regard to FDIC indemnification.