Note 6 - Debt and Equity Securities - Available for Sale Securities With Gross Unrealized Losses and Their Fair Value (Details) $ in Thousands	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Held-to-maturity securities have been in a continuous unrealized loss position, number of positions	1
Held-to-maturity securities have been in a continuous unrealized loss position, fair value	$ 19,538	$ 0
Held-to-maturity securities have been in a continuous unrealized loss position, unrealized loss	2,327
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, fair value	19,538
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses	2,327
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, fair value	0
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 0
Securities have been in a continuous unrealized loss position, number of positions	73	77
Securities have been in a continuous unrealized loss position, fair value	$ 426,979	$ 500,808
Securities have been in a continuous unrealized loss position, fair value	11,719	9,912
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	332,315	408,587
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	5,191	7,032
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	94,664	92,221
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 6,528	$ 2,880
Corporate Debt Securities [Member]
Securities have been in a continuous unrealized loss position, number of positions	14	12
Securities have been in a continuous unrealized loss position, fair value	$ 102,910	$ 85,563
Securities have been in a continuous unrealized loss position, fair value	7,090	4,436
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	28,476	76,218
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	1,524	3,782
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	74,434	9,345
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 5,566	$ 654
Municipal Debt Securities [Member]
Held-to-maturity securities have been in a continuous unrealized loss position, number of positions	1
Held-to-maturity securities have been in a continuous unrealized loss position, fair value	$ 19,538
Held-to-maturity securities have been in a continuous unrealized loss position, unrealized loss	2,327
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, fair value	19,538
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses	2,327
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, fair value	0
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 0
Securities have been in a continuous unrealized loss position, number of positions	4	7
Securities have been in a continuous unrealized loss position, fair value	$ 16,047	$ 52,898
Securities have been in a continuous unrealized loss position, fair value	64	327
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	16,047	52,898
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	64	327
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	0	0
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 0	$ 0
Other Debt Obligations [Member]
Securities have been in a continuous unrealized loss position, number of positions	1	1
Securities have been in a continuous unrealized loss position, fair value	$ 298	$ 298
Securities have been in a continuous unrealized loss position, fair value	2	2
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	0	0
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	0	0
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	298	298
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 2	$ 2
Available for Sale Securities Excluding Mortgage Backed Securities [Member]
Securities have been in a continuous unrealized loss position, number of positions	19	20
Securities have been in a continuous unrealized loss position, fair value	$ 119,255	$ 138,759
Securities have been in a continuous unrealized loss position, fair value	7,156	4,765
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	44,523	129,116
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	1,588	4,109
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	74,732	9,643
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 5,568	$ 656
REMIC and CMO [Member]
Securities have been in a continuous unrealized loss position, number of positions	35	33
Securities have been in a continuous unrealized loss position, fair value	$ 222,807	$ 238,132
Securities have been in a continuous unrealized loss position, fair value	2,873	3,147
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	208,827	182,010
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	2,268	1,642
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	13,980	56,122
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 605	$ 1,505
GNMA [Member]
Securities have been in a continuous unrealized loss position, number of positions		1
Securities have been in a continuous unrealized loss position, fair value		$ 6,977
Securities have been in a continuous unrealized loss position, fair value		139
Securities have been in a continuous unrealized loss position, less than 12 months, fair value		6,977
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses		139
Securities have been in a continuous unrealized loss position, 12 months or more, fair value		0
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses		$ 0
FNMA [Member]
Securities have been in a continuous unrealized loss position, number of positions	18	20
Securities have been in a continuous unrealized loss position, fair value	$ 80,924	$ 102,225
Securities have been in a continuous unrealized loss position, fair value	1,605	1,762
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	74,972	75,769
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	1,250	1,043
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	5,952	26,456
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 355	$ 719
FHLMC [Member]
Securities have been in a continuous unrealized loss position, number of positions	1	3
Securities have been in a continuous unrealized loss position, fair value	$ 3,993	$ 14,715
Securities have been in a continuous unrealized loss position, fair value	85	99
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	3,993	14,715
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	85	99
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	0	0
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 0	$ 0
Collateralized Mortgage Backed Securities [Member]
Securities have been in a continuous unrealized loss position, number of positions	54	57
Securities have been in a continuous unrealized loss position, fair value	$ 307,724	$ 362,049
Securities have been in a continuous unrealized loss position, fair value	4,563	5,147
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	287,792	279,471
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	3,603	2,923
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	19,932	82,578
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 960	$ 2,224