Pension and Postretirement Benefits - Additional Information (Detail)	6 Months Ended
Jun. 30, 2016 USD ($)
SERP Plans
Defined Benefit Plan Disclosure [Line Items]
Estimated contribution of pension plans	$ 38,752,000

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.

No definition available.

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