Note 8 - Employee Benefit Plans (Details) - Net Periodic Pension Cost - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Periodic Pension Cost [Abstract]
Service cost	$ 4,216	$ 4,312	$ 4,025
Interest cost	4,823	4,859	3,889
Expected return on plan assets	(5,382)	(4,996)	(4,741)
Amortization of prior service cost (benefit)	(337)	(337)	66
Amortization of net gain from earlier periods	4,260	3,275	3,152
Net periodic pension cost	$ 7,580	$ 7,113	$ 6,391