Defined Benefit Plans - Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates (Detail) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Effect on total of service and interest cost, 1-Percentage-Point Increase	$ (0.1)
Effect on total of service and interest cost, 1-Percentage-Point Decrease	$ 0.1

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.

+ Details

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- Definition

Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate.

+ 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 (m)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

+ Details

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- Definition

Amount of increase in accumulated postretirement benefit obligation from one-percentage-point increase in assumed health care cost trend rate.

+ References

+ Details

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Namespace Prefix:	us-gaap_
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