Note 7 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Interest cost	$ 1,339	$ 1,307	$ 2,678	$ 2,614
Expected return on plan assets	(1,462)	(1,325)	(2,924)	(2,650)
Amortization of prior service cost	(84)	(84)	(168)	(168)
Amortization of net (gain) loss	1,033	1,093	2,066	2,186
Net periodic pension cost	2,022	2,068	4,044	4,136
Service cost	$ 1,196	$ 1,077	$ 2,392	$ 2,154