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Note 6 - Commitments and Contingencies (Details Textual) $ in Millions	1 Months Ended			6 Months Ended
	Jan. 31, 2015 USD ($)	Jul. 31, 2014 USD ($)	Jun. 30, 2007 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 30, 2014 USD ($)
Minimum [Member] | Voluntary Cleanup Program [Member] | Subsequent Event [Member]
Environmental Remediation Expense				$ 0.3
Minimum [Member]
Estimated Cost of Epa Selected Remedy				$ 169.0
Estimated Time to Complete Selected Epa Remedy				2 years
Maximum [Member] | Voluntary Cleanup Program [Member] | Subsequent Event [Member]
Environmental Remediation Expense				$ 2.4
Maximum [Member]
Estimated Cost of Epa Selected Remedy				$ 1,760.0
Estimated Time to Complete Selected Epa Remedy				28 years
Portland Harbor Natural Resources Trustee Council [Member]
Loss Contingency, Accrual, Current						$ 0.4
Loss Contingency Accrual, Payments		$ 0.2
Voluntary Cleanup Program [Member] | Estimated [Member]
Accrual for Environmental Loss Contingencies				$ 0.4
Litigation Settlement, Amount			$ 0.2
Amount Spent To Complete Work Specified In Work Plans					$ 0.1
Amount Projected For Year To Complete Work Specified In Work Plans				$ 0.1
Number Of Potentially Responsible Parties				100
Insurance Recoveries	$ 2.6
Letters of Credit Outstanding, Amount				$ 2.1

X

- Definition

Amount projected for the current year to complete work specified in work plans for source control work.

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Total costs accrued as of the balance sheet date for environmental loss contingencies.

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