Note 16 - Benefit Plans (Details Textual) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employer Contribution under Medical and Dental Plan			$ 18,290	$ 14,660	$ 14,992
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement, Total	[1]		10,920	(0)	(0)
Payment for Pension Benefits			1,017	9,400
Defined Benefit Plan, Amortization of Gain (Loss)			(843)	(802)	(883)
Defined Benefit Plan, Plan Assets, Amount, Ending Balance		$ 0	$ 0	$ 61,870	58,014
Equity and Real Estate [Member] | Minimum [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		75.00%	75.00%
Equity and Real Estate [Member] | Maximum [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		85.00%	85.00%
Savings Plan 401(k) [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match				50.00%
Defined Contribution Plan Percentage of Eligible Compensation				6.00%
Defined Contribution Plan, Cost			$ 4,791	$ 4,193	$ 3,600
Pension Plan [Member]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement, Total		$ 10,920
Defined Benefit Plan, Amortization of Gain (Loss)			(843)
Defined Benefit Plan, Plan Assets, Amount, Ending Balance		$ 0	$ 0	$ 61,870

[1] Represents pre-tax settlement charges related to the termination of the Company’s domestic pension plan in the fourth quarter of 2019.