Note 8 - Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Service cost - benefits earned during the period	$ 57,000	$ 48,000	$ 81,000
Interest cost on projected benefit obligation	988,000	951,000	1,001,000
Expected return on plan assets	(1,188,000)	(1,343,000)	(1,395,000)
Recognized actuarial loss	1,288,000	327,000
Settlement loss	445,000	460,000	208,000
Net periodic pension cost after settlements	1,329,000	888,000	217,000
Recognized Actuarial Loss [Member]
Recognized actuarial loss	$ 1,027,000	$ 772,000	$ 322,000