Note 6 - Investment Securities (Details) - Investment Securities (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Securities Available-for-Sale
Securities available-for-sale, amortized cost	$ 1,197,922	$ 1,324,408
Securities available-for-sale, gross unrealized gains	10,956	6,326
Securities available-for-sale, gross unrealized losses	5,196	11,799
Securities available-for-sale	1,203,682us-gaap_AvailableForSaleSecurities	1,318,935us-gaap_AvailableForSaleSecurities
US Treasury Securities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	349,830	664,206
Securities available-for-sale, gross unrealized gains	353	63
Securities available-for-sale, gross unrealized losses		265
Securities available-for-sale	350,183	664,004
Collateralized Mortgage Backed Securities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	756,758	549,296
Securities available-for-sale, gross unrealized gains	3,904	1,393
Securities available-for-sale, gross unrealized losses	333	6,386
Securities available-for-sale	760,329	544,303
Collateralized Mortgage Obligations [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	74	79
Securities available-for-sale, gross unrealized losses	32	34
Securities available-for-sale	42	45
Corporate Debt Securities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	74,946	94,943
Securities available-for-sale, gross unrealized gains	730	776
Securities available-for-sale, gross unrealized losses	1,165	1,247
Securities available-for-sale	74,511	94,472
Mutual Funds [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	6,000	6,000
Securities available-for-sale, gross unrealized losses	79	134
Securities available-for-sale	5,921	5,866
Preferred Stock of Government Sponsored Entities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	6,686	6,276
Securities available-for-sale, gross unrealized gains	844	681
Securities available-for-sale, gross unrealized losses	3,584	3,733
Securities available-for-sale	3,946	3,224
Other Equity Securities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	3,628
Securities available-for-sale, gross unrealized gains	5,125
Securities available-for-sale, gross unrealized losses	3
Securities available-for-sale	8,750	7,021
Asset-backed Securities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost		3,608
Securities available-for-sale, gross unrealized gains		3,413
Securities available-for-sale		$ 7,021

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

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Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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