Note 17 - Other Employee Benefit Plans (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	6.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount			$ 10,445,000
Defined Contribution Plan, Cost	$ 8,114,000	$ 10,737,000	20,655,000
Minimum [Member]
Defined Contribution Plan, Employer Discretionary Contribution Percent	1.00%
Maximum [Member]
Defined Contribution Plan, Employer Discretionary Contribution Percent	6.00%
Retiree Health Benefit Act of 1992 [Member]
Multiemployer Plan, Employer Contribution, Cost, Total	$ 5,383,000	6,042,000	6,829,000
Multiemployer Plans, Withdrawal Obligation	56,039,000
Non Pension Multiemployer Plans [Member]
Letters of Credit Outstanding, Amount	17,421,000	18,669,000	$ 19,860,000
Long Term Disability Member [Member]
Defined Benefit Plan, Benefit Obligation, Ending Balance	$ 11,374	$ 12,749