Pension and Postretirement Benefits - Additional Information (Detail) - USD ($)		3 Months Ended
Jun. 30, 2018	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Contribution made to qualified pension plans	$ 25,000,000
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution made to qualified pension plans		$ 150,000,000
Estimated contribution to pension plans, remainder of financal year		0
Nonqualified Pension Plan [Member] \| Underfunded Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated contribution to pension plans		$ 12,400,000

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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- Definition

Amount of contributions received and expected to be received by defined benefit plan from employer in current 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 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920

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- Definition

Amount of contributions expected to be received by defined benefit plan from employer in fiscal year. Excludes contributions paid by employer in current fiscal year.

+ References

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- Definition

Amount of discretionary contributions made by an employer to a defined contribution plan.

+ References

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