Schedule of Measurement Dates (Detail)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Benefit Obligation
Defined Benefit Plan Disclosure [Line Items]
Measurement Dates	12/31/2012	12/31/2011
Fair Value Of Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Measurement Dates	12/31/2012	12/31/2011

The date(s) used to measure (at least the majority of) plan assets and benefit obligations for defined benefit pension and other postretirement benefit plans. Disclosure required by FAS 132R paragraph 5k prior to being amended by FAS 158.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph k

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

Name:	us-gaap_DefinedBenefitPlanMeasurementDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration