Note 3 - Investment Securities (Details) - Amortized cost and fair value of securities, by contractual maturity (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Maturity in years:
Securities Available for Sale, Amortized Cost, 1 year or less	$ 69,203	$ 40,380
Securities Available for Sale, Fair Value, 1 year or less	69,604	40,686
Securities Held to Maturity, Amortized Cost, 1 year or less	11,182	10,265
Securities Held to Maturity, Fair Value, 1 year or less	11,441	10,496
Securities Available for Sale, Amortized Cost, Over 1 to 5 years	426,099	309,293
Securities Available for Sale, Fair Value, Over 1 to 5 years	425,485	312,480
Securities Held to Maturity, Amortized Cost, Over 1 to 5 years	162,937	167,162
Securities Held to Maturity, Fair Value, Over 1 to 5 years	166,079	171,769
Securities Available for Sale, Amortized Cost, Over 5 to 10 years	71,015	59,817
Securities Available for Sale, Fair Value, Over 5 to 10 years	72,718	63,540
Securities Held to Maturity, Amortized Cost, Over 5 to 10 years	282,150	227,603
Securities Held to Maturity, Fair Value, Over 5 to 10 years	281,073	236,608
Securities Available for Sale, Amortized Cost, Over 10 years	98,696	110,919
Securities Available for Sale, Fair Value, Over 10 years	103,051	120,467
Securities Held to Maturity, Amortized Cost, Over 10 years	269,083	279,004
Securities Held to Maturity, Fair Value, Over 10 years	257,760	286,973
Securities Available for Sale, Amortized Cost, Subtotal	665,013	520,409
Securities Available for Sale, Fair Value, Subtotal	670,858	537,173
Securities Held to Maturity, Amortized Cost, Subtotal	725,352	684,034
Securities Held to Maturity, Fair Value, Subtotal	716,353	705,846
Securities Available for Sale, Amortized Cost, Mortgage-backed securities and residential collateralized mortgage obligations	328,918	276,767
Securities Available for Sale, Fair Value, Mortgage-backed securities and residential collateralized mortgage obligations	323,197	282,182
Securities Held to Maturity, Amortized Cost, Mortgage-backed securities and residential collateralized mortgage obligations	409,263	472,007
Securities Held to Maturity, Fair Value, Mortgage-backed securities and residential collateralized mortgage obligations	408,593	478,711
Securities Available for Sale, Amortized Cost, Other securities	2,873	2,915
Securities Available for Sale, Fair Value, Other securities	10,833	6,281
Securities Available for Sale, Amortized Cost, Total	996,804	800,091
Securities Available for Sale, Fair Value, Total	1,004,888	825,636
Securities Held to Maturity, Amortized Cost, Total	1,134,615	1,156,041
Securities Held to Maturity, Fair Value, Total	$ 1,124,946	$ 1,184,557