Schedule of Asset Allocation Policy and Ranges for Overall Risk and Return Objectives of Portfolio (Detail)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Assets allocation	21.00%
Permitted Range, minimum	10.00%
Permitted Range, maximum	30.00%
Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Assets allocation	76.00%
Permitted Range, minimum	70.00%
Permitted Range, maximum	90.00%
Other
Defined Benefit Plan Disclosure [Line Items]
Assets allocation	3.00%	3.00%
Permitted Range, minimum	0.00%
Permitted Range, maximum	10.00%

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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 1

-Subparagraph (d)(i)

-URI http://asc.fasb.org/extlink&oid=35743120&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=35743120&loc=d3e2446-114920

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

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