Schedule of Weighted Average Assumptions (Detail)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension
Pension and Other Postretirement Benefits Disclosure [Line Items]
Discount rate	4.25%	5.17%
Rate of increase in future compensation levels	4.50%	5.00%
Discount rate	5.17%	4.24%	5.14%
Rate of increase in future compensation levels	5.00%	5.00%	5.00%
Expected long-term rate of return on assets	7.00%	7.00%	7.25%
Postretirement Benefits
Pension and Other Postretirement Benefits Disclosure [Line Items]
Discount rate	3.83%	4.42%
Discount rate	4.42%	3.54%	4.44%

The interest rate used to adjust for the time value of money for the plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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Expected rate of compensation increases (for pay-related plans).

+ 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 (k)(2)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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The interest rate used to adjust for the time value of money.

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An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Long-Term Rate of Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512013

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Expected rate of compensation increases (for pay-related plans).

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-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

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