Weighted Average Assumptions used in Determining Net Periodic Benefit Cost of Health and Welfate Plan (Detail) (Post-Retirement Benefits)	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.50%	3.90%	4.70%
Current medical trend rate	7.50%	8.00%	9.00%
Ultimate trend rate	5.00%	5.00%	5.00%
Year when ultimate trend rate will be reached	2018	2018	2015

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

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- Details

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- Definition

The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

+ 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 (l)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Health Care Cost Trend Rate

-URI http://asc.fasb.org/extlink&oid=6514820

+ Details

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- Definition

The ultimate trend rate for health care costs.

+ References

+ Details

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- Definition

Year the ultimate health care cost trend rate is expected to be reached, in CCYY format.

+ References

+ Details

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