Pension and Other Postretirement Benefits - Additional Information (Detail) - Other Postretirement Benefit Plans [Member] - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plans And Other Postretirement Benefit Plans [Line Items]
Decrease in liability due to remeasurement	$ 4,632
Curtailment gain	$ 15	$ 0

Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]

No definition available.

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- Definition

Amount of (increase) decrease to benefit obligation of defined benefit plan from remeasurement due to settlement. Excludes decrease to benefit obligation for settlement payment.

+ 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 (a)(10)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

+ Details

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- Definition

Amount of gain (loss) recognized in net periodic benefit (cost) credit from event reducing expected years of future service of present employees or eliminating accrual of defined benefits for some or all future services of present employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(7)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)(7)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920

+ Details

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- Details

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