Note 4 - Debt and Equity Securities - Available for Sale Securities With Gross Unrealized Losses and Their Fair Value (Details) $ in Thousands	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Held-to-maturity securities have been in a continuous unrealized loss position, number of positions	1	1
Held-to-maturity securities have been in a continuous unrealized loss position, fair value	$ 19,612	$ 19,538
Held-to-maturity securities have been in a continuous unrealized loss position, unrealized loss	2,254	2,327
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, fair value	19,612	19,538
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses	2,254	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	$ 0
Securities have been in a continuous unrealized loss position, number of positions	67	73
Securities have been in a continuous unrealized loss position, fair value	$ 391,849	$ 426,979
Securities have been in a continuous unrealized loss position, fair value	10,977	11,719
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	287,537	332,315
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	4,479	5,191
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	104,312	94,664
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 6,498	$ 6,528
Municipal Debt Securities [Member]
Held-to-maturity securities have been in a continuous unrealized loss position, number of positions	1	1
Held-to-maturity securities have been in a continuous unrealized loss position, fair value	$ 19,612	$ 19,538
Held-to-maturity securities have been in a continuous unrealized loss position, unrealized loss	2,254	2,327
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, fair value	19,612	19,538
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses	2,254	2,327
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, fair value	0	0
Held-to-maturity 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, number of positions		4
Securities have been in a continuous unrealized loss position, fair value		$ 16,047
Securities have been in a continuous unrealized loss position, fair value		64
Securities have been in a continuous unrealized loss position, less than 12 months, fair value		16,047
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses		64
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
Corporate Debt Securities [Member]
Securities have been in a continuous unrealized loss position, number of positions	14	14
Securities have been in a continuous unrealized loss position, fair value	$ 103,694	$ 102,910
Securities have been in a continuous unrealized loss position, fair value	6,306	7,090
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	19,209	28,476
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	791	1,524
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	84,485	74,434
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 5,515	$ 5,566
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	$ 299	$ 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	299	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	15	19
Securities have been in a continuous unrealized loss position, fair value	$ 103,993	$ 119,255
Securities have been in a continuous unrealized loss position, fair value	6,308	7,156
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	19,209	44,523
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	791	1,588
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	84,784	74,732
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 5,517	$ 5,568
REMIC and CMO [Member]
Securities have been in a continuous unrealized loss position, number of positions	34	35
Securities have been in a continuous unrealized loss position, fair value	$ 208,825	$ 222,807
Securities have been in a continuous unrealized loss position, fair value	3,154	2,873
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	195,016	208,827
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	2,516	2,268
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	13,809	13,980
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 638	$ 605
FNMA [Member]
Securities have been in a continuous unrealized loss position, number of positions	17	18
Securities have been in a continuous unrealized loss position, fair value	$ 75,059	$ 80,924
Securities have been in a continuous unrealized loss position, fair value	1,432	1,605
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	69,340	74,972
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	1,089	1,250
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	5,719	5,952
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 343	$ 355
FHLMC [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	$ 3,972	$ 3,993
Securities have been in a continuous unrealized loss position, fair value	83	85
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	3,972	3,993
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	83	85
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	52	54
Securities have been in a continuous unrealized loss position, fair value	$ 287,856	$ 307,724
Securities have been in a continuous unrealized loss position, fair value	4,669	4,563
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	268,328	287,792
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	3,688	3,603
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	19,528	19,932
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 981	$ 960