Retirement Plans - Additional Information (Detail) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Compensation And Retirement Disclosure [Abstract]
Corporation's estimated contribution for funded pension plans in 2019	$ 40
Corporation's contribution for funded pension plan during the year to date	$ 10

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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