Note 7 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Service cost	$ 1,196	$ 1,077
Interest cost	1,339	1,307
Expected return on plan assets	(1,462)	(1,325)
Amortization of prior service benefit	(84)	(84)
Amortization of net loss	1,033	1,093
Net periodic benefit cost	$ 2,022	$ 2,068