Note 7 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Service cost	$ 1,077	$ 1,054	$ 3,231	$ 3,162
Interest cost	1,307	1,206	3,921	3,618
Expected return on plan assets	(1,325)	(1,345)	(3,975)	(4,036)
Amortization of prior service cost	(84)	(84)	(252)	(253)
Amortization of net loss	1,093	1,065	3,279	3,195
Net periodic pension cost	$ 2,068	$ 1,896	$ 6,204	$ 5,686