Note 4 - Investment Securities - Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Securities available-for-sale, amortized cost	$ 1,317,012	$ 1,595,723
Securities available-for-sale, gross unrealized gains	12,301	6,552
Securities available-for-sale, gross unrealized losses	14,968	15,923
Securities available-for-sale	1,314,345	1,586,352	[1]
US Treasury Securities [Member]
Securities available-for-sale, amortized cost	489,839	284,678
Securities available-for-sale, gross unrealized gains	35	5
Securities available-for-sale, gross unrealized losses	857	395
Securities available-for-sale	489,017	284,288
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale, amortized cost	400,000	150,000
Securities available-for-sale, gross unrealized gains
Securities available-for-sale, gross unrealized losses	9,669	1,840
Securities available-for-sale	390,331	148,160
Collateralized Mortgage Backed Securities [Member]
Securities available-for-sale, amortized cost	339,241	1,073,108
Securities available-for-sale, gross unrealized gains	309	560
Securities available-for-sale, gross unrealized losses	3,290	11,399
Securities available-for-sale	336,260	1,062,269
Collateralized Mortgage Obligations [Member]
Securities available-for-sale, amortized cost	48	63
Securities available-for-sale, gross unrealized gains
Securities available-for-sale, gross unrealized losses	20	27
Securities available-for-sale	28	36
Corporate Debt Securities [Member]
Securities available-for-sale, amortized cost	74,965	74,955
Securities available-for-sale, gross unrealized gains	247	425
Securities available-for-sale, gross unrealized losses	862	1,525
Securities available-for-sale	74,350	73,855
Mutual Funds [Member]
Securities available-for-sale, amortized cost	6,500	6,000
Securities available-for-sale, gross unrealized gains
Securities available-for-sale, gross unrealized losses	270	167
Securities available-for-sale	6,230	5,833
Preferred Stock of Government Sponsored Entities [Member]
Securities available-for-sale, amortized cost	2,811	2,811
Securities available-for-sale, gross unrealized gains	4,497	633
Securities available-for-sale, gross unrealized losses		228
Securities available-for-sale	7,308	3,216	[2]
Other Equity Securities [Member]
Securities available-for-sale, amortized cost	3,608	4,108
Securities available-for-sale, gross unrealized gains	7,213	4,929
Securities available-for-sale, gross unrealized losses		342
Securities available-for-sale	$ 10,821	$ 8,695	[2]

[1] Preferred stock of government sponsored entities and other equity securities as of December 31, 2015 were reclassified as level 1 rather than level 2 as originally classified due to the availability of quoted prices in active markets.

[2] Preferred stock of government sponsored entities and other equity securities as of December 31, 2015 were reclassified as level 1 rather than level 2 as originally classified due to the availability of quoted prices in active markets.