Note 3 - Investment Securities (Details) - Investment Securities (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
Jun. 30, 2013	Dec. 31, 2012
Note 3 - Investment Securities (Details) - Investment Securities [Line Items]
Held-to-Maturity Securities Amortized Cost	$ 555,464	$ 496,141
Held-to-Maturity Securities Gross Unrealized Gains	2,132	5,276
Held-to-Maturity Securities Gross Unrealized (Losses)	(14,442)	(839)
Held-to-Maturity Securities Estimated Fair Value	543,154	500,578
Available-for-Sale Securities Amortized Cost	181,496	190,920
Available-for-Sale Securities Gross Unrealized Gains	645	808
Available-for-Sale Securities Gross Unrealized (Losses)	(4,610)	(386)
Available-for-Sale Securities Estimated Fair Value	177,531	191,342
US Government Agencies Debt Securities [Member]
Note 3 - Investment Securities (Details) - Investment Securities [Line Items]
Held-to-Maturity Securities Amortized Cost	313,050	288,098
Held-to-Maturity Securities Gross Unrealized Gains	33	135
Held-to-Maturity Securities Gross Unrealized (Losses)	(8,322)	(679)
Held-to-Maturity Securities Estimated Fair Value	304,761	287,554
Available-for-Sale Securities Amortized Cost	163,989	152,708
Available-for-Sale Securities Gross Unrealized Gains		65
Available-for-Sale Securities Gross Unrealized (Losses)	(4,599)	(292)
Available-for-Sale Securities Estimated Fair Value	159,390	152,481
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Note 3 - Investment Securities (Details) - Investment Securities [Line Items]
Held-to-Maturity Securities Amortized Cost	43	49
Held-to-Maturity Securities Gross Unrealized Gains	2	1
Held-to-Maturity Securities Estimated Fair Value	45	50
Available-for-Sale Securities Amortized Cost	1,898	20,436
Available-for-Sale Securities Gross Unrealized Gains	180	287
Available-for-Sale Securities Gross Unrealized (Losses)		(89)
Available-for-Sale Securities Estimated Fair Value	2,078	20,634
US States and Political Subdivisions Debt Securities [Member]
Note 3 - Investment Securities (Details) - Investment Securities [Line Items]
Held-to-Maturity Securities Amortized Cost	241,751	207,374
Held-to-Maturity Securities Gross Unrealized Gains	2,097	5,140
Held-to-Maturity Securities Gross Unrealized (Losses)	(6,120)	(160)
Held-to-Maturity Securities Estimated Fair Value	237,728	212,354
Available-for-Sale Securities Amortized Cost	1,272	2,989
Available-for-Sale Securities Gross Unrealized Gains	1
Available-for-Sale Securities Gross Unrealized (Losses)	(11)	(1)
Available-for-Sale Securities Estimated Fair Value	1,262	2,988
Other Securities [Member]
Note 3 - Investment Securities (Details) - Investment Securities [Line Items]
Held-to-Maturity Securities Amortized Cost	620	620
Held-to-Maturity Securities Estimated Fair Value	620	620
Available-for-Sale Securities Amortized Cost	14,337	14,787
Available-for-Sale Securities Gross Unrealized Gains	464	456
Available-for-Sale Securities Gross Unrealized (Losses)		(4)
Available-for-Sale Securities Estimated Fair Value	$ 14,801	$ 15,239

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