Segment Information - Additional Information (Detail)	12 Months Ended
Dec. 31, 2012 Employees Segment	Dec. 31, 2011 Employees	Dec. 31, 2010 Employees
Segment Reporting Information [Line Items]
Number of reportable segments	4
Maximum percentage of revenue for which an individual customer accounts for	13.40%
Number of individual customer accounting for greater than ten percent of consolidated revenue	1	0	0

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

No definition available.

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration