Investment in Seven Hills - Additional Information (Detail) - Seven Hills - Variable Interest Entity, Not Primary Beneficiary - Equity Method Investee - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule of Equity Method Investments [Line Items]
Cost of paperboard	$ 11.1	$ 11.3	$ 22.9	$ 22.4
Purchase commitments			$ 36.3

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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