Note 7 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Domestic Tax Authority [Member]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		$ 112,000,000
State and Local Jurisdiction [Member] | Valuation Allowance, Operating Loss Carryforwards [Member]
Deferred Tax Assets, Valuation Allowance		1,700,000	$ 2,100,000
State and Local Jurisdiction [Member]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		153,500,000
Capital Loss Carryforward [Member]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount		(400,000)	(700,000)
Scenario, Forecast [Member]
Unrecognized Tax Benefits, Period Increase (Decrease)	$ (300,000)
Deferred Tax Assets, Valuation Allowance		1,683,000	2,052,000
Increase (Decrease) in Pension Plan Obligations		5,800,000	(17,100,000)	$ 16,000,000
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		(3,528,000)	10,403,000	(9,761,000)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax		2,300,000	(6,700,000)	6,200,000
Income Taxes Paid, Net		1,800,000	400,000	$ 500,000
Accrued Income Taxes		800,000	1,900,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		700,000	1,300,000
Liability for Uncertain Tax Positions, Current		$ 300,000	$ 600,000