Note 3 - Investment Securities (Details) - Securities with Unrealized Losses (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Held-to-Maturity
Held-to-Maturity Securities Less Than 12 Months Estimated Fair Value	$ 386,821
Held-to-Maturity Securities Less Than 12 Months Gross Unrealized Losses	(5,086)
Held-to-Maturity Securities 12 Months or More Estimated Fair Value	97,246
Held-to-Maturity Securities 12 Months or More Gross Unrealized Losses	(1,790)
Held-to-Maturity Securities Estimated Fair Value	484,068
Held-to-Maturity Securities Gross Unrealized Losses	(6,877)
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	219,637
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(2,134)
Available-for-Sale Securities 12 Months or More Estimated Fair Value	59,080
Available-for-Sale Securities 12 Months or More Gross Unrealized Losses	(1,224)
Available-for-Sale Securities Estimated Fair Value	278,717
Available-for-Sale Securities Gross Unrealized Losses	(3,358)
US Government Agencies Debt Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Less Than 12 Months Estimated Fair Value	316,956
Held-to-Maturity Securities Less Than 12 Months Gross Unrealized Losses	(4,059)
Held-to-Maturity Securities 12 Months or More Estimated Fair Value	72,610
Held-to-Maturity Securities 12 Months or More Gross Unrealized Losses	(1,343)
Held-to-Maturity Securities Estimated Fair Value	389,566
Held-to-Maturity Securities Gross Unrealized Losses	(5,403)
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	211,696
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(2,092)
Available-for-Sale Securities 12 Months or More Estimated Fair Value	59,080
Available-for-Sale Securities 12 Months or More Gross Unrealized Losses	(1,224)
Available-for-Sale Securities Estimated Fair Value	270,776
Available-for-Sale Securities Gross Unrealized Losses	(3,316)
Collateralized Mortgage Backed Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Less Than 12 Months Estimated Fair Value	27,239
Held-to-Maturity Securities Less Than 12 Months Gross Unrealized Losses	(602)
Held-to-Maturity Securities Estimated Fair Value	27,239
Held-to-Maturity Securities Gross Unrealized Losses	(602)
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	1,570
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(21)
Available-for-Sale Securities Estimated Fair Value	1,570
Available-for-Sale Securities Gross Unrealized Losses	(21)
US States and Political Subdivisions Debt Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Less Than 12 Months Estimated Fair Value	42,626
Held-to-Maturity Securities Less Than 12 Months Gross Unrealized Losses	(425)
Held-to-Maturity Securities 12 Months or More Estimated Fair Value	24,636
Held-to-Maturity Securities 12 Months or More Gross Unrealized Losses	(447)
Held-to-Maturity Securities Estimated Fair Value	67,263
Held-to-Maturity Securities Gross Unrealized Losses	(872)
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	699
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(2)
Available-for-Sale Securities Estimated Fair Value	699
Available-for-Sale Securities Gross Unrealized Losses	(2)
US Treasury Securities [Member]
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	3,991
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(10)
Available-for-Sale Securities Estimated Fair Value	3,991
Available-for-Sale Securities Gross Unrealized Losses	(10)
Other Securities [Member]
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	1,681
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(9)
Available-for-Sale Securities Estimated Fair Value	1,681
Available-for-Sale Securities Gross Unrealized Losses	$ (9)