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Enviromental matters (Details 2) (USD $)	9 Months Ended
	Sep. 30, 2012
Portland Harbor site [Member]
Site contingency [Line Items]
Estimated investigative costs	$ 70,000,000
Environmental litigation number 1 [Member]
Site contingency [Line Items]
Site contingency, low estimate, loss exposure	500,000
Site contingency, loss exposure, high estimate	11,000,000
Estimated proportional share of cleanup liability	50.00%
Accrual for environmental loss contingencies	1,300,000
Environmental litigation number 2 [Member]
Site contingency [Line Items]
Site contingency, low estimate, loss exposure	340,000
Site contingency, loss exposure, high estimate	6,400,000
Accrual for environmental loss contingencies	6,400,000
Estimated investigative costs	6,400,000
Environmental litigation number 3 [Member]
Site contingency [Line Items]
Site contingency, loss exposure not accrued, best estimate	8,000,000
Environmental litigation number 4 [Member]
Site contingency [Line Items]
Site contingency, loss exposure not accrued, best estimate	$ 100,000

X

- Definition

Estimated investigative costs.

+ References

No definition available.

+ Details

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X

- Definition

The estimated proportional share of the clean-up costs.

+ References

No definition available.

+ Details

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X

- Definition

High-end of the range estimate of the loss exposure for reasonably possible environmental contingencies at an individual site.

+ References

No definition available.

+ Details

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X

- Definition

Low-end of the range estimate of the loss exposure for reasonable possible environmental contingencies at an individual site.

+ References

No definition available.

+ Details

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 25

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 30

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 96-1

-Paragraph 161

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 5: 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=6952336&loc=d3e14326-108349

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- Definition

Best estimate of the loss exposure for reasonably possible environmental contingencies at an individual site for which no accrual has been recorded.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 96-1

-Paragraph 163

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 30

-Section 50

-Paragraph 10

-Subparagraph (c),(d)(2)

-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

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