Pension Benefits - Changes in Benefit Obligation and Fair Value of Benefit Plans Assets (Footnote) (Detail) $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($)
Compensation and Retirement Disclosure [Abstract]
Amortized from accumulated other comprehensive (loss) income into net periodic benefit cost	$ 0.5

Amount included in accumulated other comprehensive income (AOCI) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position, including gain (loss), prior service cost (credit), and transition asset (obligation).

No definition available.

Name:	us-gaap_DefinedBenefitPlanAmountToBeAmortizedFromAccumulatedOtherComprehensiveIncomeLossNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration