Note 8 - Benefit Plans - Defined Benefit Plans Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in benefit obligation
Benefit obligation at beginning of year	$ 24,790,000	$ 25,470,000
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
Recognized actuarial loss	1,288,000	327,000
Benefits paid	(1,865,000)	(2,006,000)
Benefit obligation at end of year	25,258,000	24,790,000	25,470,000
Changes in plan assets
Fair value of plan assets at beginning of year	15,865,000	17,386,000
Actual return on assets	1,291,000	(515,000)
Employer contributions	500,000	1,000,000
Benefits paid	(1,865,000)	(2,006,000)
Fair value of plan assets at end of year	15,791,000	15,865,000	$ 17,386,000
Funded status at end of year	(9,467,000)	(8,925,000)
Amounts recognized in consolidated balance sheet
Long-term pension liability	(9,467,000)	(8,925,000)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss	$ 9,819,000	$ 10,106,000