Employee Benefits - Additional Information (Detail) (USD $) In Billions, unless otherwise specified	3 Months Ended
Mar. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Amount paid in severance benefits over the period	$ 0.1
Post employment benefits liability	0.9
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan contributions by employer	$ 0.4

Liability for amount due employees, in addition to wages and any other money that employers owe employees, when their employment ends through a layoff or other termination. For example, a company may provide involuntarily terminated employees with a lump sum payment equal to one week's salary for every year of employment.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Other Postemployment Benefits

-URI http://asc.fasb.org/extlink&oid=6519534

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 112

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

Name:	us-gaap_SupplementalUnemploymentBenefitsSeveranceBenefits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant