Weighted Average Asset Allocations (Detail)	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan weighted average asset allocation	100.00%	100.00%
Equity Securities
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan weighted average asset allocation	64.00%	62.00%
Debt Securities
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan weighted average asset allocation	22.00%	22.00%
Real Estate
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan weighted average asset allocation	3.00%	3.00%
Other
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan weighted average asset allocation	11.00%	13.00%

Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

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)

-URI http://asc.fasb.org/extlink&oid=21915506&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)(1)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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