Note 7 - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Service cost	$ 1,077	$ 1,054	$ 2,154	$ 2,108
Interest cost	1,307	1,206	2,614	2,412
Expected return on plan assets	(1,325)	(1,345)	(2,650)	(2,691)
Amortization of prior service cost	(84)	(84)	(168)	(169)
Amortization of net (gain) loss	1,093	1,065	2,186	2,130
Net periodic pension cost	$ 2,068	$ 1,896	$ 4,136	$ 3,790