Note 4 - Securities - Available for Sale Securities With Gross Unrealized Losses and Their Fair Value (Details) $ in Thousands	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Held-to-maturity securities have been in a continuous unrealized loss position, number of positions	2	2
Held-to-maturity securities have been in a continuous unrealized loss position, fair value	$ 28,822	$ 27,306
Held-to-maturity securities have been in a continuous unrealized loss position, unrealized loss	479	2,144
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, fair value
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, fair value	28,822	27,306
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 479	$ 2,144
Securities have been in a continuous unrealized loss position, number of positions	78	87
Securities have been in a continuous unrealized loss position, fair value	$ 551,633	$ 589,648
Securities have been in a continuous unrealized loss position, unrealized losses	17,311	24,131
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	135,231	143,932
Securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses	1,773	2,845
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	416,402	445,716
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 15,538	$ 21,286
US States and Political Subdivisions 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	$ 21,096	$ 19,940
Held-to-maturity securities have been in a continuous unrealized loss position, unrealized loss	256	1,557
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, fair value
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, fair value	21,096	19,940
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 256	$ 1,557
Securities have been in a continuous unrealized loss position, number of positions		3
Securities have been in a continuous unrealized loss position, fair value		$ 4,220
Securities have been in a continuous unrealized loss position, unrealized losses
Securities have been in a continuous unrealized loss position, less than 12 months, fair value		4,220
Securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses
Securities have been in a continuous unrealized loss position, 12 months or more, fair value
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses
Other Debt Obligations [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	$ 21,096	$ 19,940
Held-to-maturity securities have been in a continuous unrealized loss position, unrealized loss	256	1,557
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, fair value
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, fair value	21,096	19,940
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 256	$ 1,557
Securities have been in a continuous unrealized loss position, number of positions	27	30
Securities have been in a continuous unrealized loss position, fair value	$ 207,278	$ 209,507
Securities have been in a continuous unrealized loss position, unrealized losses	9,634	13,110
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	105,315	110,085
Securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses	1,597	2,533
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	101,963	99,422
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 8,037	$ 10,577
FNMA [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	$ 7,726	$ 7,366
Held-to-maturity securities have been in a continuous unrealized loss position, unrealized loss	223	587
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, fair value
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, fair value	7,726	7,366
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 223	$ 587
Securities have been in a continuous unrealized loss position, number of positions	12	14
Securities have been in a continuous unrealized loss position, fair value	$ 77,992	$ 85,046
Securities have been in a continuous unrealized loss position, unrealized losses	1,465	2,448
Securities have been in a continuous unrealized loss position, less than 12 months, fair value		6,372
Securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses		17
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	77,992	78,674
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 1,465	$ 2,431
Collateralized Mortgage Backed 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	$ 7,726	$ 7,366
Held-to-maturity securities have been in a continuous unrealized loss position, unrealized loss	223	587
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, fair value
Held-to-maturity securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, fair value	7,726	7,366
Held-to-maturity securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 223	$ 587
Securities have been in a continuous unrealized loss position, number of positions	51	57
Securities have been in a continuous unrealized loss position, fair value	$ 344,355	$ 380,141
Securities have been in a continuous unrealized loss position, unrealized losses	7,677	11,021
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	29,916	33,847
Securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses	176	312
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	314,439	346,294
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 7,501	$ 10,709
Corporate Debt Securities [Member]
Securities have been in a continuous unrealized loss position, number of positions	16	16
Securities have been in a continuous unrealized loss position, fair value	$ 121,382	$ 118,535
Securities have been in a continuous unrealized loss position, unrealized losses	8,618	11,465
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	19,419	19,113
Securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses	581	888
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	101,963	99,422
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 8,037	$ 10,577
Collateralized Loan Obligations [Member]
Securities have been in a continuous unrealized loss position, number of positions	11	11
Securities have been in a continuous unrealized loss position, fair value	$ 85,896	$ 86,752
Securities have been in a continuous unrealized loss position, unrealized losses	1,016	1,645
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	85,896	86,752
Securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses	1,016	1,645
Securities have been in a continuous unrealized loss position, 12 months or more, fair value
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses
REMIC and CMO [Member]
Securities have been in a continuous unrealized loss position, number of positions	36	39
Securities have been in a continuous unrealized loss position, fair value	$ 215,761	$ 243,756
Securities have been in a continuous unrealized loss position, unrealized losses	5,351	7,177
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	20,259	17,308
Securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses	79	200
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	195,502	226,448
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 5,272	$ 6,977
FHLMC [Member]
Securities have been in a continuous unrealized loss position, number of positions	3	3
Securities have been in a continuous unrealized loss position, fair value	$ 50,602	$ 51,288
Securities have been in a continuous unrealized loss position, unrealized losses	861	1,396
Securities have been in a continuous unrealized loss position, less than 12 months, fair value	9,657	10,116
Securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses	97	95
Securities have been in a continuous unrealized loss position, 12 months or more, fair value	40,945	41,172
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses	$ 764	$ 1,301
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		$ 51
Securities have been in a continuous unrealized loss position, unrealized losses
Securities have been in a continuous unrealized loss position, less than 12 months, fair value		51
Securities have been in a continuous unrealized loss position, less than 12 months, unrealized losses
Securities have been in a continuous unrealized loss position, 12 months or more, fair value
Securities have been in a continuous unrealized loss position, 12 months or more, unrealized losses