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Note 7 - Commitments and Contingencies (Details Textual)	1 Months Ended
	Jan. 31, 2017 USD ($)	Jul. 31, 2014 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2014 USD ($)
Number Of Potentially Responsible Parties			100
Estimated Cost of EPA Selected Remedy	$ 1,000,000,000
Estimated Time to Complete Selected EPA Remedy	13 years
Letters of Credit Outstanding, Amount			$ 2,000,000
Portland Harbor Natural Resources Trustee Council [Member]
Loss Contingency, Accrual, Current				$ 400,000
Loss Contingency Accrual, Payments		$ 200,000
Voluntary Cleanup Program [Member] | Minimum [Member]
Loss Contingency, Estimate of Possible Loss			0
Voluntary Cleanup Program [Member] | Maximum [Member]
Loss Contingency, Estimate of Possible Loss			$ 1,500,000
Lower Willamette Group [Member]
Number Of Potentially Responsible Parties			14

X

- Definition

The estimated cost of the remedy selected by EPA.

+ References

No definition available.

+ Details

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X

- Definition

The estimated amount of time to complete the selected EPA remedy.

+ References

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X

- Definition

Number of potentially responsible parties for Portland Harbor Superfund site.

+ References

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X

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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- Definition

Amount of loss contingency liability expected to be resolved within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

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X

- Definition

Amount of cash outflow reducing loss contingency liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

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- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

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