Note 3 - Investment Securities (Details) - Securities with Unrealized Losses (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Held-to-Maturity
Held-to-Maturity Securities Less Than 12 Months Estimated Fair Value	$ 378,075
Held-to-Maturity Securities Less Than 12 Months Gross Unrealized Losses	(13,358)
Held-to-Maturity Securities 12 Months or More Estimated Fair Value	10,344
Held-to-Maturity Securities 12 Months or More Gross Unrealized Losses	(279)
Held-to-Maturity Securities Estimated Fair Value	388,419
Held-to-Maturity Securities Gross Unrealized Losses	(13,637)
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	155,973
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(4,909)
Available-for-Sale Securities 12 Months or More Estimated Fair Value	973
Available-for-Sale Securities 12 Months or More Gross Unrealized Losses	(28)
Available-for-Sale Securities Estimated Fair Value	156,946
Available-for-Sale Securities Gross Unrealized Losses	(4,937)
US Government Agencies Debt Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Less Than 12 Months Estimated Fair Value	289,718
Held-to-Maturity Securities Less Than 12 Months Gross Unrealized Losses	(8,334)
Held-to-Maturity Securities 12 Months or More Estimated Fair Value	8,754
Held-to-Maturity Securities 12 Months or More Gross Unrealized Losses	(246)
Held-to-Maturity Securities Estimated Fair Value	298,472
Held-to-Maturity Securities Gross Unrealized Losses	(8,580)
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	154,760
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(4,904)
Available-for-Sale Securities 12 Months or More Estimated Fair Value	973
Available-for-Sale Securities 12 Months or More Gross Unrealized Losses	(28)
Available-for-Sale Securities Estimated Fair Value	155,733
Available-for-Sale Securities Gross Unrealized Losses	(4,932)
US States and Political Subdivisions Debt Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Less Than 12 Months Estimated Fair Value	88,357
Held-to-Maturity Securities Less Than 12 Months Gross Unrealized Losses	(5,024)
Held-to-Maturity Securities 12 Months or More Estimated Fair Value	1,590
Held-to-Maturity Securities 12 Months or More Gross Unrealized Losses	(334)
Held-to-Maturity Securities Estimated Fair Value	89,947
Held-to-Maturity Securities Gross Unrealized Losses	(5,057)
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	1,213
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(5)
Available-for-Sale Securities 12 Months or More Estimated Fair Value	0
Available-for-Sale Securities 12 Months or More Gross Unrealized Losses	0
Available-for-Sale Securities Estimated Fair Value	1,213
Available-for-Sale Securities Gross Unrealized Losses	$ (5)