Note 4 - Investment Securities (Details) - Temporarily Impaired Securities (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value	$ 376,601	$ 877,208
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses	3,998	64,562
Securities Available-for-Sale - Less than 12 Months - No. of Issuances	8	30
Securities Available-for-Sale - 12 Months or longer - Fair Value	494,754	106,378
Securities Available-for-Sale - 12 Months or longer - Unrealized Losses	7,801	5,246
Securities Available-for-Sale - 12 Months or longer - No. of issuances	22	19
Securities Available-for-Sale - Fair Value	871,355	983,586
Securities Available-for-Sale - Unrealized Losses	11,799	69,808
Securities Available-for-Sale - No. of issuances	30	49
US Treasury Securities [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value	374,153	75,064
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses	265	1
Securities Available-for-Sale - Less than 12 Months - No. of Issuances	6	1
Securities Available-for-Sale - Fair Value	374,153	75,064
Securities Available-for-Sale - Unrealized Losses	265	1
Securities Available-for-Sale - No. of issuances	6	1
Collateralized Mortgage Backed Securities [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value		792,012
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses		64,526
Securities Available-for-Sale - Less than 12 Months - No. of Issuances		25
Securities Available-for-Sale - 12 Months or longer - Fair Value	425,090	272
Securities Available-for-Sale - 12 Months or longer - Unrealized Losses	6,386	2
Securities Available-for-Sale - 12 Months or longer - No. of issuances	16	7
Securities Available-for-Sale - Fair Value	425,090	792,284
Securities Available-for-Sale - Unrealized Losses	6,386	64,528
Securities Available-for-Sale - No. of issuances	16	32
Collateralized Mortgage Obligations [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value		68
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses		4
Securities Available-for-Sale - Less than 12 Months - No. of Issuances		2
Securities Available-for-Sale - 12 Months or longer - Fair Value	45	301
Securities Available-for-Sale - 12 Months or longer - Unrealized Losses	34	50
Securities Available-for-Sale - 12 Months or longer - No. of issuances	1	3
Securities Available-for-Sale - Fair Value	45	369
Securities Available-for-Sale - Unrealized Losses	34	54
Securities Available-for-Sale - No. of issuances	1	5
Corporate Debt Securities [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value		9,970
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses		30
Securities Available-for-Sale - Less than 12 Months - No. of Issuances		1
Securities Available-for-Sale - 12 Months or longer - Fair Value	63,753	100,081
Securities Available-for-Sale - 12 Months or longer - Unrealized Losses	1,247	4,919
Securities Available-for-Sale - 12 Months or longer - No. of issuances	4	8
Securities Available-for-Sale - Fair Value	63,753	110,051
Securities Available-for-Sale - Unrealized Losses	1,247	4,949
Securities Available-for-Sale - No. of issuances	4	9
Mutual Funds [Member]
Securities Available-for-Sale
Securities Available-for-Sale - 12 Months or longer - Fair Value	5,866	5,724
Securities Available-for-Sale - 12 Months or longer - Unrealized Losses	134	275
Securities Available-for-Sale - 12 Months or longer - No. of issuances	1	1
Securities Available-for-Sale - Fair Value	5,866	5,724
Securities Available-for-Sale - Unrealized Losses	134	275
Securities Available-for-Sale - No. of issuances	1	1
Preferred Stock of Government Sponsored Entities [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value	2,448
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses	3,733
Securities Available-for-Sale - Less than 12 Months - No. of Issuances	2
Securities Available-for-Sale - Fair Value	2,448
Securities Available-for-Sale - Unrealized Losses	3,733
Securities Available-for-Sale - No. of issuances	2
Mortgage Backed Securities Non Agency [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value		94
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses		1
Securities Available-for-Sale - Less than 12 Months - No. of Issuances		1
Securities Available-for-Sale - Fair Value		94
Securities Available-for-Sale - Unrealized Losses		$ 1
Securities Available-for-Sale - No. of issuances		1

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Amount of unrealized loss on securities classified as available-for-sale that have been in a loss position for twelve months or longer.

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