Note 8 - Employee Benefit Plans - Defined Benefit Plan Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair value of plan assets at beginning of year	$ 17,038
Fair value of plan assets at end of year	23,428	$ 17,038
Amortization of prior service cost	71	72	$ 72
Pension Plan [Member]
Projected benefit obligation at beginning of year	21,059	20,427	19,324
Service cost	692	694	620
Interest cost	743	757	669
Actuarial loss	1,417	198	798
Benefits paid	(419)	(1,017)	(984)
Projected benefit obligation at end of year	23,492	21,059	20,427
Fair value of plan assets at beginning of year	17,038	16,131	17,130
Actual return on plan assets	2,302	1,113	(155)
Employer contribution	4,507	811	140
Benefits paid	(419)	(1,017)	(984)
Fair value of plan assets at end of year	23,428	17,038	16,131
Funded status at the end of the year	(64)	(4,021)	(4,296)
Deferred tax asset	13	1,407	1,504
Other liabilities	(64)	(4,021)	(4,296)
Total amounts recognized in the Consolidated Balance Sheet	(51)	(2,614)	(2,792)
Net gain (loss)	(7,923)	(8,250)	(8,627)
Prior service cost	340	449	559
Deferred tax asset	1,592	2,730	2,798
Amount recognized	(5,991)	(5,071)	(5,270)
Benefit obligation	(23,492)	(21,059)	(20,427)
Fair value of assets	23,428	17,038	16,131
Unrecognized net actuarial loss	7,923	8,250	8,627
Unrecognized prior service cost	(340)	(449)	(559)
Deferred tax liability	(1,579)	(1,323)	(1,294)
Prepaid benefit cost included in other assets	5,940	2,457	2,478
Expected return on plan assets	(1,097)	(1,110)	(1,166)
Amortization of prior service cost	(110)	(110)	(110)
Recognized net actuarial loss	540	572	414
Net periodic benefit cost	768	803	427
Net (gain) loss	(328)	(377)	1,705
Amortization of prior service cost	110	110	110
Deferred income tax expense (benefit)	46	93	(635)
Total recognized	(172)	(174)	1,180
Total recognized in net periodic benefit cost and other comprehensive loss	$ 550	$ 536	$ 2,242
Discount rate used for net periodic pension cost	4.00%	4.00%	3.75%
Discount rate used for disclosure	3.50%	4.00%	4.00%
Expected return on plan assets	7.50%	7.50%	7.50%
Rate of compensation increase	3.00%	3.00%	3.00%