Pension and Other Postretirement Benefits - Summary of Plan Asset Allocations (Detail)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan Assets, Equity	28.00%	28.00%
Plan Assets, Fixed Income	66.00%	65.00%
Plan Assets, Other	6.00%	7.00%
Plan Assets, Total	100.00%	100.00%
Target Plan Asset Allocation, Equity	27.00%	27.00%
Target Plan Asset Allocation, Fixed Income	68.00%	68.00%
Target Plan Asset Allocation, Other	5.00%	5.00%
Target Plan Asset Allocation, Total	100.00%	100.00%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan Assets, Equity	63.00%	64.00%
Plan Assets, Fixed Income	34.00%	34.00%
Plan Assets, Cash	3.00%	2.00%
Plan Assets, Total	100.00%	100.00%
Target Plan Asset Allocation, Equity	60.00%	60.00%
Target Plan Asset Allocation, Fixed Income	35.00%	35.00%
Target Plan Asset Allocation, Cash	5.00%	5.00%
Target Plan Asset Allocation, Total	100.00%	100.00%

Defined benefit plan cash.

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- Definition

Defined benefit plan target allocation percent of assets equity securities.

+ References

No definition available.

+ Details

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- Definition

Defined benefit plan target allocation percentage one.

+ References

No definition available.

+ Details

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- Definition

Defined benefit plan target allocation percentage of assets cash.

+ References

No definition available.

+ Details

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- Definition

Defined benefit plan target allocation percentage of assets fixed income.

+ References

No definition available.

+ Details

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- Definition

Percentage of defined benefit plan fixed income assets.

+ References

No definition available.

+ Details

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- Definition

Percentage of defined benefit plan other plan assets.

+ References

No definition available.

+ Details

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- Definition

Percentage of defined benefits plan equity securities.

+ References

No definition available.

+ Details

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- Definition

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.

+ References

No definition available.

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- Definition

Target allocation of investments of this type to total plan assets presented on a weighted average basis.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)(i)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2446-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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- Definition

Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2446-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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