Defined Contribution Plans, Pension and Other Post-Retirement Benefit Plans - Expected Future Benefit Payments of Pension and Other Post-Retirement Benefit Plans (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
2018	$ 4,065
2019	4,275
2020	4,461
2021	4,499
2022	4,467
2023 to 2026	$ 23,547

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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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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