Retirement Plans and Other Post-Retirement Benefits - Schedule of Targeted Range of Investment Allocations of Plan Assets (Detail)	12 Months Ended
Dec. 31, 2016
Domestic Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation for the plan assets, minimum	35.00%
Target allocation for the plan assets, maximum	45.00%
International Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation for the plan assets, minimum	8.00%
Target allocation for the plan assets, maximum	14.00%
Real Estate Investment Trusts (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation for the plan assets, minimum	2.00%
Target allocation for the plan assets, maximum	6.00%
Fixed Income, Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation for the plan assets, minimum	55.00%
Target allocation for the plan assets, maximum	35.00%

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Target allocation maximum percentage 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=65897934&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=65897934&loc=d3e1928-114920

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Target allocation minimum percentage 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 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Reference 2: 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=65897934&loc=d3e2446-114920

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