Note 3 - Investment Securities (Details) - Securities with Unrealized Losses (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Held-to-Maturity
Held-to-Maturity Securities Less Than 12 Months Estimated Fair Value	$ 277,344
Held-to-Maturity Securities Less Than 12 Months Gross Unrealized Losses	(3,047)
Held-to-Maturity Securities 12 Months or More Estimated Fair Value	176,598
Held-to-Maturity Securities 12 Months or More Gross Unrealized Losses	(3,856)
Held-to-Maturity Securities Estimated Fair Value	453,942
Held-to-Maturity Securities Gross Unrealized Losses	(6,903)
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	139,349
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(993)
Available-for-Sale Securities 12 Months or More Estimated Fair Value	93,901
Available-for-Sale Securities 12 Months or More Gross Unrealized Losses	(1,897)
Available-for-Sale Securities Estimated Fair Value	233,250
Available-for-Sale Securities Gross Unrealized Losses	(2,890)
US Government Agencies Debt Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Less Than 12 Months Estimated Fair Value	228,195
Held-to-Maturity Securities Less Than 12 Months Gross Unrealized Losses	(2,194)
Held-to-Maturity Securities 12 Months or More Estimated Fair Value	142,085
Held-to-Maturity Securities 12 Months or More Gross Unrealized Losses	(2,857)
Held-to-Maturity Securities Estimated Fair Value	370,280
Held-to-Maturity Securities Gross Unrealized Losses	(5,051)
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	134,656
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(983)
Available-for-Sale Securities 12 Months or More Estimated Fair Value	93,901
Available-for-Sale Securities 12 Months or More Gross Unrealized Losses	(1,897)
Available-for-Sale Securities Estimated Fair Value	228,557
Available-for-Sale Securities Gross Unrealized Losses	(2,880)
Collateralized Mortgage Backed Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Less Than 12 Months Estimated Fair Value	26,586
Held-to-Maturity Securities Less Than 12 Months Gross Unrealized Losses	(519)
Held-to-Maturity Securities Estimated Fair Value	26,586
Held-to-Maturity Securities Gross Unrealized Losses	(519)
US States and Political Subdivisions Debt Securities [Member]
Held-to-Maturity
Held-to-Maturity Securities Less Than 12 Months Estimated Fair Value	22,563
Held-to-Maturity Securities Less Than 12 Months Gross Unrealized Losses	(334)
Held-to-Maturity Securities 12 Months or More Estimated Fair Value	34,513
Held-to-Maturity Securities 12 Months or More Gross Unrealized Losses	(999)
Held-to-Maturity Securities Estimated Fair Value	57,076
Held-to-Maturity Securities Gross Unrealized Losses	(1,333)
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	(3)
Available-for-Sale Securities Estimated Fair Value	699
Available-for-Sale Securities Gross Unrealized Losses	(3)
US Treasury Securities [Member]
Available-for-Sale
Available-for-Sale Securities Less Than 12 Months Estimated Fair Value	3,994
Available-for-Sale Securities Less Than 12 Months Gross Unrealized Losses	(7)
Available-for-Sale Securities Estimated Fair Value	3,994
Available-for-Sale Securities Gross Unrealized Losses	$ (7)