Note 3 - Investment Securities (Details) - Investment Securities (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
Jun. 30, 2014	Dec. 31, 2013
Note 3 - Investment Securities (Details) - Investment Securities [Line Items]
Held-to-Maturity Securities Amortized Cost	$ 799,963	$ 745,688
Held-to-Maturity Securities Gross Unrealized Gains	7,341	2,232
Held-to-Maturity Securities Gross Unrealized (Losses)	(6,903)	(16,475)
Held-to-Maturity Securities Estimated Fair Value	800,401	731,445
Available-for-Sale Securities Amortized Cost	272,548	217,217
Available-for-Sale Securities Gross Unrealized Gains	678	652
Available-for-Sale Securities Gross Unrealized (Losses)	(2,890)	(5,592)
Available-for-Sale Securities Estimated Fair Value	270,336	212,277
US Government Agencies Debt Securities [Member]
Note 3 - Investment Securities (Details) - Investment Securities [Line Items]
Held-to-Maturity Securities Amortized Cost	449,201	395,198
Held-to-Maturity Securities Gross Unrealized Gains	1,028	50
Held-to-Maturity Securities Gross Unrealized (Losses)	(5,051)	(10,535)
Held-to-Maturity Securities Estimated Fair Value	445,178	384,713
Available-for-Sale Securities Amortized Cost	241,545	183,781
Available-for-Sale Securities Gross Unrealized Gains	(254)	8
Available-for-Sale Securities Gross Unrealized (Losses)	(2,880)	(5,572)
Available-for-Sale Securities Estimated Fair Value	238,411	178,217
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Note 3 - Investment Securities (Details) - Investment Securities [Line Items]
Held-to-Maturity Securities Amortized Cost	32,204	34,425
Held-to-Maturity Securities Gross Unrealized Gains	176	17
Held-to-Maturity Securities Gross Unrealized (Losses)	(519)	(442)
Held-to-Maturity Securities Estimated Fair Value	31,861	34,000
Available-for-Sale Securities Amortized Cost	1,636	1,735
Available-for-Sale Securities Gross Unrealized Gains	322	156
Available-for-Sale Securities Estimated Fair Value	1,958	1,891
US States and Political Subdivisions Debt Securities [Member]
Note 3 - Investment Securities (Details) - Investment Securities [Line Items]
Held-to-Maturity Securities Amortized Cost	317,938	315,445
Held-to-Maturity Securities Gross Unrealized Gains	6,137	2,165
Held-to-Maturity Securities Gross Unrealized (Losses)	(1,333)	(5,498)
Held-to-Maturity Securities Estimated Fair Value	322,742	312,112
Available-for-Sale Securities Amortized Cost	6,910	7,860
Available-for-Sale Securities Gross Unrealized Gains	13	4
Available-for-Sale Securities Gross Unrealized (Losses)	(3)	(3)
Available-for-Sale Securities Estimated Fair Value	6,920	7,861
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	18,456	19,840
Available-for-Sale Securities Gross Unrealized Gains	597	484
Available-for-Sale Securities Gross Unrealized (Losses)		(1)
Available-for-Sale Securities Estimated Fair Value	19,053	20,323
US Treasury Securities [Member]
Note 3 - Investment Securities (Details) - Investment Securities [Line Items]
Available-for-Sale Securities Amortized Cost	4,001	4,001
Available-for-Sale Securities Gross Unrealized (Losses)	(7)	(16)
Available-for-Sale Securities Estimated Fair Value	$ 3,994	$ 3,985

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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