Retirement Benefits - Benefits Expected to Be Paid from Pension and Other Postretirement Benefit Plans, Which Reflect Future Years of Services (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2019	$ 41,211
2020	40,842
2021	42,339
2022	43,469
2023	44,516
2024-2028	233,796
Defined Benefit Plan Expected Future Benefit Payments	446,173
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2019	1,924
2020	1,702
2021	1,545
2022	1,486
2023	1,463
2024-2028	6,468
Defined Benefit Plan Expected Future Benefit Payments	$ 14,588

Defined Benefit Plan, Expected Future Benefit Payments

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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.

+ References

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- Definition

Amount of benefits for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following latest fiscal year.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

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- Definition

Amount of benefits for defined benefit plan expected to be paid in next fiscal year following latest fiscal year.

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Amount of benefits for defined benefit plan expected to be paid in fifth fiscal year following latest fiscal year.

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Amount of benefits for defined benefit plan expected to be paid in fourth fiscal year following latest fiscal year.

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Amount of benefits for defined benefit plan expected to be paid in third fiscal year following latest fiscal year.

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Amount of benefits for defined benefit plan expected to be paid in second fiscal year following latest fiscal year.

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