Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Commitments And Contingencies
Reserves for environmental remediation liabilities	$ 15.0	$ 15.6
Accounts payable and accrued liabilities of environmental remediation reserves	3.9	4.0
Asset retirement obligations	5.6	5.3
Asset Retirement Obligation, current	0.8	0.9
Asset Retirement Obligation, non-current	$ 4.8	$ 4.4

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

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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Carrying value of the obligation (known or estimated) arising from requirements to perform activities to remediate one or more sites, payable in twelve months or in the next operating cycle if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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