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Commitments and Contingencies - Additional Information (Detail) (USD $) | 1 Months Ended | 9 Months Ended
--- | --- | ---
Jun. 30, 2007 | Sep. 30, 2013
Commitments And Contingencies Disclosure [Abstract] |  |
Company made payments to Lower Willamette Group as interim settlement | $ 175,000 |
Maximum amount anticipated to spend for further Source Control work |  | 100,000
Adjustment related to contingency liability in Portland Harbor matters |  | 0
Total stand by letters of credit |  | $ 3,100,000

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