Note 3 - Investment Securities (Details) - Amortized Cost and Fair Value of Securities, by Contractual Maturity (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Maturity in years:
Securities Available for Sale, Amortized Cost, 1 year or less	$ 45,444	$ 75,385
Securities Available for Sale, Fair Value, 1 year or less	45,671	75,609
Securities Held to Maturity, Amortized Cost, 1 year or less	13,767	9,639
Securities Held to Maturity, Fair Value, 1 year or less	14,233	9,900
Securities Available for Sale, Amortized Cost, Over 1 to 5 years	625,789	536,333
Securities Available for Sale, Fair Value, Over 1 to 5 years	629,181	538,111
Securities Held to Maturity, Amortized Cost, Over 1 to 5 years	216,979	187,051
Securities Held to Maturity, Fair Value, Over 1 to 5 years	220,062	189,827
Securities Available for Sale, Amortized Cost, Over 5 to 10 years	362,884	66,669
Securities Available for Sale, Fair Value, Over 5 to 10 years	366,119	68,166
Securities Held to Maturity, Amortized Cost, Over 5 to 10 years	270,071	314,630
Securities Held to Maturity, Fair Value, Over 5 to 10 years	273,124	310,104
Securities Available for Sale, Amortized Cost, Over 10 years	67,722	87,722
Securities Available for Sale, Fair Value, Over 10 years	72,471	90,484
Securities Held to Maturity, Amortized Cost, Over 10 years	203,901	246,988
Securities Held to Maturity, Fair Value, Over 10 years	205,873	233,017
Securities Available for Sale, Amortized Cost, Subtotal	1,101,839	766,109
Securities Available for Sale, Fair Value, Subtotal	1,113,442	772,370
Securities Held to Maturity, Amortized Cost, Subtotal	704,718	758,308
Securities Held to Maturity, Fair Value, Subtotal	713,292	742,848
Securities Available for Sale, Amortized Cost, Mortgage-backed securities and residential collateralized mortgage obligations	269,686	302,729
Securities Available for Sale, Fair Value, Mortgage-backed securities and residential collateralized mortgage obligations	260,659	290,497
Securities Held to Maturity, Amortized Cost, Mortgage-backed securities and residential collateralized mortgage obligations	330,323	373,991
Securities Held to Maturity, Fair Value, Mortgage-backed securities and residential collateralized mortgage obligations	328,093	369,828
Securities Available for Sale, Amortized Cost, Other securities	2,843	2,853
Securities Available for Sale, Fair Value, Other securities	17,261	16,514
Securities Available for Sale, Amortized Cost, Total	1,374,368	1,071,691
Securities Available for Sale, Fair Value, Total	1,391,362	1,079,381
Securities Held to Maturity, Amortized Cost, Total	1,035,041	1,132,299
Securities Held to Maturity, Fair Value, Total	$ 1,041,385	$ 1,112,676