Note 6 - Accrued Retirement Benefits (Details Textual)	1 Months Ended	12 Months Ended		24 Months Ended
	Oct. 31, 2014 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2012 a
Lipoa Point [Member]
Proceeds from Sale of Productive Assets	$ 19,800,000
Cost of Real Estate Sales	$ 400,000
Minimum [Member]
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year		$ 0	$ 2,800,000
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Actuarial Gain (Loss), before Tax		28,700,000	$ 25,600,000
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year		1,000,000
Defined Benefit Plan, Additional Security to Support Unfunded Liabilities		23,900,000
Defined Benefit Plan, Area of Real Estate Property Pledged as Security | a				8,400
Defined Benefit Plan, Period for Release of Real Estate Property Pledged as Security				5 years
Proceeds from Sale of Productive Assets		52,000
Cost of Real Estate Sales		$ 1,759,000	$ 1,294,000