Note 2 - Investment Securities (Details) - Amortized Cost and Estimated Market Value of Securities by Contractual Maturity (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Maturity in years:
Securities Available for Sale, Amortized Cost, 1 year or less	$ 75,385	$ 40,380
Securities Available for Sale, Estimated Market Value, 1 year or less	75,609	40,686
Securities Held to Maturity, Amortized Cost, 1 year or less	9,639	10,265
Securities Held to Maturity, Estimated Market Value, 1 year or less	9,900	10,496
Securities Available for Sale, Amortized Cost, Over 1 to 5 years	536,333	309,293
Securities Available for Sale, Estimated Market Value, Over 1 to 5 years	538,111	312,480
Securities Held to Maturity, Amortized Cost, Over 1 to 5 years	187,051	167,162
Securities Held to Maturity, Estimated Market Value, Over 1 to 5 years	189,827	171,769
Securities Available for Sale, Amortized Cost, Over 5 to 10 years	66,669	59,817
Securities Available for Sale, Estimated Market Value, Over 5 to 10 years	68,166	63,540
Securities Held to Maturity, Amortized Cost, Over 5 to 10 years	314,630	227,603
Securities Held to Maturity, Estimated Market Value, Over 5 to 10 years	310,104	236,608
Securities Available for Sale, Amortized Cost, Over 10 years	87,722	110,919
Securities Available for Sale, Estimated Market Value, Over 10 years	90,484	120,467
Securities Held to Maturity, Amortized Cost, Over 10 years	246,988	279,004
Securities Held to Maturity, Estimated Market Value, Over 10 years	233,017	286,973
Securities Available for Sale, Amortized Cost, Subtotal	766,109	520,409
Securities Available for Sale, Estimated Market Value, Subtotal	772,370	537,173
Securities Held to Maturity, Amortized Cost, Subtotal	758,308	684,034
Securities Held to Maturity, Estimated Market Value, Subtotal	742,848	705,846
Securities Available for Sale, Amortized Cost, Mortgage-backed securities and residential collateralized mortgage obligations	302,729	276,767
Securities Available for Sale, Estimated Market Value, Mortgage-backed securities and residential collateralized mortgage obligations	290,497	282,182
Securities Held to Maturity, Amortized Cost, Mortgage-backed securities and residential collateralized mortgage obligations	373,991	472,007
Securities Held to Maturity, Estimated Market Value, Mortgage-backed securities and residential collateralized mortgage obligations	369,828	478,711
Securities Available for Sale, Amortized Cost, Other securities	2,853	2,915
Securities Available for Sale, Estimated Market Value, Other securities	16,514	6,281
Securities Available for Sale, Amortized Cost, Total	1,071,691	800,091
Securities Available for Sale, Estimated Market Value, Total	1,079,381	825,636
Securities Held to Maturity, Amortized Cost, Total	1,132,299	1,156,041
Securities Held to Maturity, Estimated Market Value, Total	$ 1,112,676	$ 1,184,557