Note 8 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability		$ 146,000,000
Increase (Decrease) in Obligation, Pension Benefits	$ (1,100,000)	7,400,000	$ (600,000)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax, Total	(788,000)	4,520,000	361,000
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax, Total	300,000	2,900,000	200,000
Income Taxes Paid, Net, Total	34,200,000	2,000,000	$ 14,600,000
Prepaid Taxes	0	$ 13,791,000
State and Local Jurisdiction [Member]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 51,900,000