Note 3 - Investment Securities (Details) - Amortized Cost and Fair Value of Investment Securities Classified as Held-To-Maturity and Available-For-Sale: (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Held-to-Maturity
Held-to-Maturity Securities Amortized Cost	$ 745,688	$ 496,141
Held-to-Maturity Securities Gross Unrealized Gains	2,232	5,276
Held-to-Maturity Securities Gross Unrealized (Losses)	(16,475)	(839)
Held-to-Maturity Securities Estimated Fair Value	731,445	500,578
Available-for-Sale
Available-for-Sale Securities Amortized Cost	217,217	190,920
Available-for-Sale Securities Gross Unrealized Gains	652	808
Available-for-Sale Securities Gross Unrealized (Losses)	(5,592)	(386)
Available-for-Sale Securities Estimated Fair Value	212,277	191,342
US Government Agencies Debt Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Amortized Cost	395,198	288,098
Held-to-Maturity Securities Gross Unrealized Gains	50	135
Held-to-Maturity Securities Gross Unrealized (Losses)	(10,535)	(679)
Held-to-Maturity Securities Estimated Fair Value	384,713	287,554
Available-for-Sale
Available-for-Sale Securities Amortized Cost	183,781	152,708
Available-for-Sale Securities Gross Unrealized Gains	8	65
Available-for-Sale Securities Gross Unrealized (Losses)	(5,572)	(292)
Available-for-Sale Securities Estimated Fair Value	178,217	152,481
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Held-to-Maturity
Held-to-Maturity Securities Amortized Cost	34,425	49
Held-to-Maturity Securities Gross Unrealized Gains	17	1
Held-to-Maturity Securities Gross Unrealized (Losses)	(442)
Held-to-Maturity Securities Estimated Fair Value	34,000	50
Available-for-Sale
Available-for-Sale Securities Amortized Cost	1,735	20,436
Available-for-Sale Securities Gross Unrealized Gains	156	287
Available-for-Sale Securities Gross Unrealized (Losses)		(89)
Available-for-Sale Securities Estimated Fair Value	1,891	20,634
US States and Political Subdivisions Debt Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Amortized Cost	315,445	207,374
Held-to-Maturity Securities Gross Unrealized Gains	2,165	5,140
Held-to-Maturity Securities Gross Unrealized (Losses)	(5,498)	(160)
Held-to-Maturity Securities Estimated Fair Value	312,112	212,354
Available-for-Sale
Available-for-Sale Securities Amortized Cost	7,860	2,989
Available-for-Sale Securities Gross Unrealized Gains	4
Available-for-Sale Securities Gross Unrealized (Losses)	(3)	(1)
Available-for-Sale Securities Estimated Fair Value	7,861	2,988
Other Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Amortized Cost	620	620
Held-to-Maturity Securities Estimated Fair Value	620	620
Available-for-Sale
Available-for-Sale Securities Amortized Cost	19,840	14,787
Available-for-Sale Securities Gross Unrealized Gains	484	456
Available-for-Sale Securities Gross Unrealized (Losses)	(1)	(4)
Available-for-Sale Securities Estimated Fair Value	20,323	15,239
US Treasury Securities [Member]
Available-for-Sale
Available-for-Sale Securities Amortized Cost	4,001
Available-for-Sale Securities Gross Unrealized (Losses)	(16)
Available-for-Sale Securities Estimated Fair Value	$ 3,985