Note 3 - Investment Securities (Details) - Amortized cost, unrealized gains and losses, and fair value - held to maturity investment securities portfolio (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Note 3 - Investment Securities (Details) - Amortized cost, unrealized gains and losses, and fair value - held to maturity investment securities portfolio [Line Items]
Amortized Cost	$ 1,134,615	$ 1,156,041
Gross Unrealized Gains	11,601	30,322
Gross Unrealized Losses	(21,270)	(1,806)
Fair Value	1,124,946	1,184,557
US Government-sponsored Enterprises Debt Securities [Member]
Note 3 - Investment Securities (Details) - Amortized cost, unrealized gains and losses, and fair value - held to maturity investment securities portfolio [Line Items]
Amortized Cost	2,256	3,232
Gross Unrealized Gains	10	43
Fair Value	2,266	3,275
Residential Mortgage Backed Securities [Member]
Note 3 - Investment Securities (Details) - Amortized cost, unrealized gains and losses, and fair value - held to maturity investment securities portfolio [Line Items]
Amortized Cost	64,404	72,807
Gross Unrealized Gains	986	2,090
Gross Unrealized Losses	(488)	(10)
Fair Value	64,902	74,887
US States and Political Subdivisions Debt Securities [Member]
Note 3 - Investment Securities (Details) - Amortized cost, unrealized gains and losses, and fair value - held to maturity investment securities portfolio [Line Items]
Amortized Cost	723,096	680,802
Gross Unrealized Gains	9,146	23,004
Gross Unrealized Losses	(18,155)	(1,235)
Fair Value	714,087	702,571
Residential Collateralized Mortgage Obligations [Member]
Note 3 - Investment Securities (Details) - Amortized cost, unrealized gains and losses, and fair value - held to maturity investment securities portfolio [Line Items]
Amortized Cost	344,859	399,200
Gross Unrealized Gains	1,459	5,185
Gross Unrealized Losses	(2,627)	(561)
Fair Value	$ 343,691	$ 403,824