Underlying Asset Split of Fund (Detail)	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Total underlying asset split	100.00%	100.00%
Equity
Defined Benefit Plan Disclosure [Line Items]
Total underlying asset split	70.00%	90.00%
Bonds
Defined Benefit Plan Disclosure [Line Items]
Total underlying asset split	30.00%	10.00%

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

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=28361610&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=28361610&loc=d3e2446-114920

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration