Note 4 - Loans and Allowance for Credit Losses (Detail) - Recorded investment in loans evaluated for impairment (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for credit losses:
Individually evaluated for impairment	$ 2,852	$ 2,023
Collectively evaluated for impairment	30,075	33,267
Total	32,927	35,290	38,329
Carrying value of loans:
Individually evaluated for impairment	29,023	16,124
Collectively evaluated for impairment	2,067,705	2,473,519
Purchased loans with evidence of credit deterioration	14,629	34,163
Total	2,111,357	2,523,806
Commercial [Member]
Allowance for credit losses:
Individually evaluated for impairment	1,865
Collectively evaluated for impairment	6,314	7,672
Total	8,179	7,672	9,878
Carrying value of loans:
Individually evaluated for impairment	5,153
Collectively evaluated for impairment	334,963	398,446
Total	340,116	398,446
Commercial Real Estate Loans [Member]
Allowance for credit losses:
Individually evaluated for impairment	134	229
Collectively evaluated for impairment	9,938	10,382
Total	10,072	10,611	9,607
Carrying value of loans:
Individually evaluated for impairment	4,161	1,399
Collectively evaluated for impairment	628,766	703,256
Total	632,927	704,655
Construction [Member]
Allowance for credit losses:
Individually evaluated for impairment		1,794
Collectively evaluated for impairment	484	582
Total	484	2,376	3,559
Carrying value of loans:
Individually evaluated for impairment		3,126
Collectively evaluated for impairment	7,984	11,454
Total	7,984	14,580
Residential Real Estate Loans [Member]
Allowance for credit losses:
Collectively evaluated for impairment	380	781
Total	380	781	617
Carrying value of loans:
Collectively evaluated for impairment	222,458	271,111
Total	222,458	271,111
Consumer Installment And Other [Member]
Allowance for credit losses:
Individually evaluated for impairment	100
Collectively evaluated for impairment	3,513	3,270
Total	3,613	3,270	6,982
Carrying value of loans:
Collectively evaluated for impairment	460,698	473,815
Total	460,698	473,815
Purchased Non-Covered Loans [Member]
Carrying value of loans:
Individually evaluated for impairment	3,029	5,611
Collectively evaluated for impairment	65,098	104,738
Purchased loans with evidence of credit deterioration	6,764	15,572
Total	74,891	125,921
Purchased Covered Loans [Member]
Allowance for credit losses:
Individually evaluated for impairment	753
Collectively evaluated for impairment	252
Total	1,005
Carrying value of loans:
Individually evaluated for impairment	16,680	5,988
Collectively evaluated for impairment	347,738	510,699
Purchased loans with evidence of credit deterioration	7,865	18,591
Total	372,283	535,278
Unallocated Financing Receivable [Member]
Allowance for credit losses:
Collectively evaluated for impairment	9,194	10,580
Total	$ 9,194	$ 10,580	$ 7,686