Note 4 - Investment Securities (Details) - Investment Securities - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Securities Available-for-Sale
Securities available-for-sale, amortized cost	$ 1,595,723	$ 1,324,408
Securities available-for-sale, gross unrealized gains	6,552	6,326
Securities available-for-sale, gross unrealized losses	15,923	11,799
Securities available-for-sale	1,586,352	1,318,935
US Treasury Securities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	284,678	664,206
Securities available-for-sale, gross unrealized gains	5	63
Securities available-for-sale, gross unrealized losses	395	265
Securities available-for-sale	284,288	664,004
US Government-sponsored Enterprises Debt Securities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	150,000
Securities available-for-sale, gross unrealized losses	1,840
Securities available-for-sale	148,160
Collateralized Mortgage Backed Securities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	1,073,108	549,296
Securities available-for-sale, gross unrealized gains	560	1,393
Securities available-for-sale, gross unrealized losses	11,399	6,386
Securities available-for-sale	1,062,269	544,303
Collateralized Mortgage Obligations [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	63	79
Securities available-for-sale, gross unrealized losses	27	34
Securities available-for-sale	36	45
Corporate Debt Securities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	74,955	94,943
Securities available-for-sale, gross unrealized gains	425	776
Securities available-for-sale, gross unrealized losses	1,525	1,247
Securities available-for-sale	73,855	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	167	134
Securities available-for-sale	5,833	5,866
Preferred Stock of Government Sponsored Entities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	2,811	6,276
Securities available-for-sale, gross unrealized gains	633	681
Securities available-for-sale, gross unrealized losses	228	3,733
Securities available-for-sale	3,216	3,224
Other Equity Securities [Member]
Securities Available-for-Sale
Securities available-for-sale, amortized cost	4,108	3,608
Securities available-for-sale, gross unrealized gains	4,929	3,413
Securities available-for-sale, gross unrealized losses	342
Securities available-for-sale	$ 8,695	$ 7,021

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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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.

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