Commitments and Contingencies - Schedule of Environmental Liability Associated with Potsdam (Detail) - USD ($) $ in Thousands	8 Months Ended	12 Months Ended
Dec. 31, 2014	Dec. 31, 2015	Apr. 30, 2014
Site Contingency [Line Items]
Ending balance		$ 5,221
Potsdam Environmental Remediation Liability [Member]
Site Contingency [Line Items]
Beginning balance	$ 5,320	5,142	$ 5,297
Revisions in estimates			(118)
Payments	(270)		(28)
Ending balance	5,142	5,221	5,320
Potsdam Environmental Remediation Liability [Member] \| Obligations Incurred [Member]
Site Contingency [Line Items]
Accretion expense			31
Potsdam Environmental Remediation Liability [Member] \| Accretion Expense [Member]
Site Contingency [Line Items]
Accretion expense	$ 92	$ 79	$ 138

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
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
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-Section 50
-Paragraph 7
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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