Note 12 - Pension and Other Postretirement Benefit Plans - Components of the Net Pension Expense for the Directors’ Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest cost	$ 902	$ 889
Directors' Plan [Member]
Service cost	42	45	$ 54
Interest cost	97	95	116
Amortization of unrecognized gain	(86)	(56)	(60)
Amortization of past service liability	40	40	40
Net pension expense	93	124	150
Current actuarial gain	(63)	(130)	(52)
Amortization of actuarial gain	86	56	60
Amortization of prior service cost	(40)	(40)	(40)
Total recognized in other comprehensive income	(17)	(114)	(32)
Total recognized in net pension expense and other comprehensive income	$ 76	$ 10	$ 118