Note 3 - Investment Securities (Details) - Amortized Cost and Fair Value of Securities, by Contractual Maturity (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Maturity in years:
Securities Available for Sale, Amortized Cost, 1 year or less	$ 35,521	$ 75,385
Securities Available for Sale, Fair Value, 1 year or less	35,862	75,609
Securities Held to Maturity, Amortized Cost, 1 year or less	8,947	9,639
Securities Held to Maturity, Fair Value, 1 year or less	9,215	9,900
Securities Available for Sale, Amortized Cost, Over 1 to 5 years	726,407	536,333
Securities Available for Sale, Fair Value, Over 1 to 5 years	728,374	538,111
Securities Held to Maturity, Amortized Cost, Over 1 to 5 years	206,687	187,051
Securities Held to Maturity, Fair Value, Over 1 to 5 years	209,237	189,827
Securities Available for Sale, Amortized Cost, Over 5 to 10 years	84,231	66,669
Securities Available for Sale, Fair Value, Over 5 to 10 years	86,679	68,166
Securities Held to Maturity, Amortized Cost, Over 5 to 10 years	299,437	314,630
Securities Held to Maturity, Fair Value, Over 5 to 10 years	298,232	310,104
Securities Available for Sale, Amortized Cost, Over 10 years	82,788	87,722
Securities Available for Sale, Fair Value, Over 10 years	86,695	90,484
Securities Held to Maturity, Amortized Cost, Over 10 years	234,877	246,988
Securities Held to Maturity, Fair Value, Over 10 years	229,265	233,017
Securities Available for Sale, Amortized Cost, Subtotal	928,947	766,109
Securities Available for Sale, Fair Value, Subtotal	937,610	772,370
Securities Held to Maturity, Amortized Cost, Subtotal	749,948	758,308
Securities Held to Maturity, Fair Value, Subtotal	745,949	742,848
Securities Available for Sale, Amortized Cost, Mortgage-backed securities and residential collateralized mortgage obligations	292,985	302,729
Securities Available for Sale, Fair Value, Mortgage-backed securities and residential collateralized mortgage obligations	282,977	290,497
Securities Held to Maturity, Amortized Cost, Mortgage-backed securities and residential collateralized mortgage obligations	360,381	373,991
Securities Held to Maturity, Fair Value, Mortgage-backed securities and residential collateralized mortgage obligations	357,878	369,828
Securities Available for Sale, Amortized Cost, Other securities	2,843	2,853
Securities Available for Sale, Fair Value, Other securities	19,701	16,514
Securities Available for Sale, Amortized Cost, Total	1,224,775	1,071,691
Securities Available for Sale, Fair Value, Total	1,240,288	1,079,381
Securities Held to Maturity, Amortized Cost, Total	1,110,329	1,132,299
Securities Held to Maturity, Fair Value, Total	$ 1,103,827	$ 1,112,676