Plan Assets at Fair Value (Parenthetical) (Detail)	Dec. 31, 2012	Dec. 31, 2011
Common/collective Trusts \| U.S. short maturity fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Percentage of fair value of investments	67.00%	67.00%
Common/collective Trusts \| U. S. Large Cap equities
Defined Benefit Plan Disclosure [Line Items]
Percentage of fair value of investments	25.00%	25.00%
Common/collective Trusts \| International equities
Defined Benefit Plan Disclosure [Line Items]
Percentage of fair value of investments	8.00%	8.00%
Mutual Funds \| Short term fixed income fund
Defined Benefit Plan Disclosure [Line Items]
Percentage of fair value of investments	100.00%	100.00%

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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