Pension and Other Postretirement Benefits - Effect of One Percentage - Point Change in Assumed Health Care Cost Trend Rates (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($)
Postemployment Benefits [Abstract]
Effect on total of service and interest cost components, 1% Increase	$ 133
Effect on postretirement benefit obligation, 1% Increase	3,203
Effect on total of service and interest cost components, 1% Decrease	(109)
Effect on postretirement benefit obligation, 1% Decrease	$ (2,640)

Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (m)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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- Definition

Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

+ References

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- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

+ References

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- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

+ References

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- References

No definition available.

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