Note 4 - Loans and Allowance for Credit Losses (Detail) - Changes in the carrying amount of impaired purchased loans (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Purchased Covered Loans [Member]
Carrying amount at the beginning of the period	$ 7,865	$ 18,591
Reductions during the period	(284)	(10,726)
Carrying amount at the end of the period	7,581	7,865
Purchased Non-Covered Loans [Member]
Carrying amount at the beginning of the period	6,764	15,572
Reductions during the period	(804)	(8,808)
Carrying amount at the end of the period	$ 5,960	$ 6,764